global warming – Cabot Institute for the Environment blog

Why 40°C is bearable in a desert but lethal in the tropics

Posted on June 2, 2023 by amanda.woodman-hardy

Phew: heat plus humidity can make Bangkok an uncomfortable place in a heatwave.
Pavel V.Khon/SHutterstock

This year, even before the northern hemisphere hot season began, temperature records were being shattered. Spain for instance saw temperatures in April (38.8°C) that would be out of the ordinary even at the peak of summer. South and south-east Asia in particular were hammered by a very persistent heatwave, and all-time record temperatures were experienced in countries such as Vietnam and Thailand (44°C and 45°C respectively). In Singapore, the more modest record was also broken, as temperatures hit 37°C. And in China, Shanghai just recorded its highest May temperature for over a century at 36.7°C.

We know that climate change makes these temperatures more likely, but also that heatwaves of similar magnitudes can have very different impacts depending on factors like humidity or how prepared an area is for extreme heat. So, how does a humid country like Vietnam cope with a 44°C heatwave, and how does it compare with dry heat, or a less hot heatwave in even-more-humid Singapore?

Weather and physiology

The recent heatwave in south-east Asia may well be remembered for its level of heat-induced stress on the body. Heat stress is mostly caused by temperature, but other weather-related factors such as humidity, radiation and wind are also important.

Our bodies gain heat from the air around us, from the sun, or from our own internal processes such as digestion and exercise. In response to this, our bodies must lose some heat. Some of this we lose directly to the air around us and some through breathing. But most heat is lost through sweating, as when the sweat on the surface of our skin evaporates it takes in energy from our skin and the air around us in the form of latent heat.

annotated diagram of person — How humans heat up and cool down.
Take from Buzan and Huber (2020) Annual Review of Earth and Planetary Sciences, Author provided

Meteorological factors affect all this. For example, being deprived of shade exposes the body to heat from direct sunlight, while higher humidity means that the rate of evaporation from our skin will decrease.

It’s this humidity that meant the recent heatwave in south-east Asia was so dangerous, as it’s already an extremely humid part of the world.

The limit of heat stress

Underlying health conditions and other personal circumstances can lead to some people being more vulnerable to heat stress. Yet heat stress can reach a limit above which all humans, even those who are not obviously vulnerable to heat risk – that is, people who are fit, healthy and well acclimatised – simply cannot survive even at a moderate level of exertion.

One way to assess heat stress is the so-called Wet Bulb Globe Temperature. In full sun conditions, that is approximately equivalent to 39°C in temperature combined with 50% relative humidity. This limit will likely have been exceeded in some places in the recent heatwave across south-east Asia.

In less humid places far from the tropics, the humidity and thus the wet bulb temperature and danger will be much lower. Spain’s heatwave in April with maximum temperatures of 38.8°C had WBGT values of “only” around 30°C, the 2022 heatwave in the UK, when temperatures exceeded 40°C, had a humidity of less than 20% and WBGT values of around 32°C.

Two of us (Eunice and Dann) were part of a team who recently used climate data to map heat stress around the world. The research highlighted regions most at risk of exceeding these thresholds, with literal hotspots including India and Pakistan, south-east Asia, the Arabian peninsula, equatorial Africa, equatorial South America and Australia. In these regions, heat stress thresholds are exceeded with increased frequency with greater global warming.

In reality, most people are already vulnerable well below the survivability thresholds, which is why we can see large death tolls in significantly cooler heat waves. Furthermore, these global analyses often do not capture some very localised extremes caused by microclimate processes. For example a certain neighbourhood in a city might trap heat more efficiently than its surroundings, or might be ventilated by a cool sea breeze, or be in the “rain shadow” of a local hill, making it less humid.

Variability and acclimatisation

The tropics typically have less variable temperatures. For example, Singapore sits almost on the equator and its daily maximum is about 32°C year round, while a typical maximum in London in mid summer is just 24°C. Yet London has a higher record temperature (40°C vs 37°C in Singapore).

Given that regions such as south-east Asia consistently have high heat stress already, perhaps that suggests that people will be well acclimatised to deal with heat. Initial reporting suggests the intense heat stress of the recent heatwave lead to surprisingly few direct deaths – but accurate reporting of deaths from indirect causes is not yet available.

On the other hand, due to the relative stability in year-round warmth, perhaps there is less preparedness for the large swings in temperature associated with the recent heatwave. Given that it is not unreasonable, even in the absence of climate change, that natural weather variability can produce significant heatwaves that break local records by several degrees Celsius, even nearing a physiological limit might be a very risky line to tread.

—————————–

This blog is written by Cabot Institute for the Environment members: Dr Alan Thomas Kennedy-Asser, Research Associate in Climate Science; Professor Dann Mitchell, Professor of Climate Science, and Dr Eunice Lo, Research Fellow in Climate Change and Health, University of Bristol. This article is republished from The Conversation under a Creative Commons license. Read the original article.

COP27: What really happened on finance, justice and Loss and Damage?

Posted on December 2, 2022April 16, 2023 by janet.crompton

The Cabot Institute for the Environment sent three delegates to the recent Conference of the Parties 27 (COP27). Drs Alix Dietzel (Sociology, Politics and International Studies); Colin Nolden (Bristol Law School); and Rachel James (Geographical Sciences) were present for most of the first week and Colin was there for the full two weeks. As the Institute has observer status with the United Nations Framework Convention on Climate Change, Alix, Rachel and Colin had the chance to engage with policy makers and climate policy experts from around the world to help promote climate action which is informed by the best evidence and research.

We asked them to give an update on their experience at COP27 and as a result, whether the pledges made at COP27 would mean that 1.5C is still achievable.

Drs Colin Nolden and Alix Dietzel at COP27.

Climate finance – Dr Colin Nolden

Colin’s research interests span sustainable energy policy, regulation and business models and interactions with secondary markets such as carbon markets and other sectors such as mobility. COP27 was an opportunity for him to talk directly to policymakers about implementing the Paris Agreement and to people directly affected by climate policy decisions.

Here are Colin’s post-COP thoughts:

“Alongside Loss and Damage, the main issue discussed at COP is climate finance for decarbonisation. The $100bn/yr pledged in Paris has never materialised and to add injury to insult, rich countries can borrow at 4%, whereas poor countries borrow at 14%, as Mia Motley, Prime Minister of Barbados, pointed out in her speech on Day 1. Under these conditions, investments in fossil fuel infrastructures pay off, but investments in renewables do not. An endless number of panel discussions and side events on ‘climate finance’ and ‘accelerating the clean energy/net zero transition’ are testament to this gap.

“Article 6 of the Paris Agreement is a mechanism to overcome this funding gap by providing the legal foundation to finance decarbonisation projects in a country in exchange for carbon credits provided by another. Whether these should lead to according adjustments in emissions inventories, as is the case under bilateral agreements using Article 6.2, is controversial. How Article 6.4 will deal with this issue is still unclear and is unlikely to be agreed on at successive COPs. Negotiations on Article 6 will determine the climate credit and finance architecture for years to come.”

Climate justice – Dr Alix Dietzel

Alix is Associate Director for Impact and Innovation at the Cabot Institute for the Environment and an environmental justice scholar. Her role at COP27 was to observe the negotiations and critically reflect on whose voices were heard and whose were left out of the discussion, as well as concentrating on whether topics such as Loss and Damage and just transition were being given adequate space and time during the negotiations.

Dr Alix Dietzel at COP27.

Here are Alix’s reflections from COP27:

“Despite much excitement over a new Loss and Damage fund, there is backsliding on commitments to lower emissions and phasing out fossil fuels. As an academic expert in just transition who went along this year hoping to make a difference, I share the anger felt around the world about this outcome.

“Attendance at COPs is strictly regulated. Parties (negotiating teams), the media, and observers (NGOs, IGOs, and UN Agencies) must all be pre-approved. Observers have access to the main plenaries and ceremonies, the pavilion exhibition spaces, and side-events. The negotiation rooms, however, are largely off limits. Most of the day is spent listening to speeches, networking, and asking questions at side-events. The main role of observers, then, is to apply indirect pressure on negotiators, report on what is happening, and network. Meaningful impact on and participation in negotiations seemed out of reach for many of the passionate people I met.

“It has long been known that who gets a say in climate change governance is skewed. As someone working on fair decision making as part of just transition, it is clear that only the most powerful voices are reflected in treaties such as the Paris Agreement. Despite being advertised as ‘Africa’s COP’, COP27 has further hampered inclusion. The run up was dogged by accusations of inflated hotel prices and concerns over surveillance, no chance to organize protests, and warnings about Egypt’s brutal police state.

“Arriving in Sharm El Sheik, there was an air of intimidation starting at the airport, where military personnel scrutinized passports. Police roadblocks featured heavily on our way to the hotel, and military officials surrounded the COP venue the next morning. Inside the venue, there were rumours we were being watched and observers were urged not to download the official app. More minor issues included voices literally not being heard due to unreliable microphones and the constant drone of airplanes overhead. Food queues were huge, and it was difficult to access water to refill our bottles. Sponsored by Coca Cola, we could buy soft drinks. Outside of COP, unless I was accompanied by a man, I faced near constant sexual harassment, hampering my ability to come and go freely.

“Who was there and who was most represented at COP27 also concerned me. The United Arab Emirates (UAE) registered the largest party delegation with more than 1,000 people, almost twice the size of the next biggest delegation, Brazil. Oil and gas lobby representatives were registered in the national delegations of 29 different countries and were larger than any single national delegation (outside of the UAE). At least 636 of those attending were lobbyists for the fossil-fuel industry. Despite the promise that COP27 would foreground African interests, the fossil lobby outnumbers any delegation from Africa. These numbers give a sense of who has power and say at these negotiations, and who does not.

“All this to say, I am not surprised at the outcomes. There is some good news in the form of a new fund for Loss and Damage – but there is no agreement yet on how much money should be paid in, by whom, and on what basis. More worryingly, the outcome document makes no mention of phasing out fossil fuels, and scant reference to the 1.5C target. Laurence Tubiana, one of the architects of the Paris Agreement, blamed the host country, Egypt, for the final decision.

“COP27 produced a text that clearly protects oil and gas petro-states and the fossil fuel industry. The final outcomes demonstrate that despite the thousands who were there to advocate for climate justice, it was the fossil fuel lobby who had most influence. As a climate justice scholar, I am deeply worried about the processes at COPs, especially given next year’s destination: The United Arab Emirates. Time is running out and watered-down commitments on emissions are at this stage deeply unjust and frankly dangerous.”

Loss and Damage – Dr Rachel James

Rachel is a climate scientist, focusing on African climate systems and developing climate science to inform and advance climate change policy. Her previous research has been designed to progress international climate policy discussions, including the COP process, and she has analysed the impacts of global mitigation goals, comparing different warming scenarios (1.5°C, 2°C and beyond). At COP27, she engaged in adaptation discussions, to learn more about how science can support national adaptation planning, to guide her new research programme “Salient”, a UKRI Future Leaders Fellowship to improve climate information for adaptation, primarily in southern Africa.

Dr Rachel James (fourth from right) at COP27.

In her previous work, Dr James has also looked at how science can support policy discussions about ‘Loss and Damage’, from climate change, and at COP27 she followed discussions on Loss and Damage, as well as taking part in a workshop to establish a network of African researchers focusing on Loss and Damage. Rachel reflects on her experience of COP and the Loss and Damage discussions:

“The COP is now a huge event, with hundreds of discussions happening simultaneously, and many thousands of people, (almost) all pushing for climate action, and acting on it in their own ways. There are lots of things going on, deals being struck, collaborations forming, alongside the official UNFCCC business.

“This was supposed to be the “COP of implementation”, as the Paris Agreement and the rulebook are already in place. Some said we were largely beyond negotiation.

“However, the Global South came ready to negotiate, particularly on Loss and Damage. They wanted a finance facility on Loss and Damage to be established. Negotiations began in the weekend before the COP, and – after negotiating all night with no food – the developing countries succeeded in getting this onto the formal agenda.

“Over the two weeks of the COP, my perception was that there was a huge shift on Loss and Damage. Once it was on the official agenda, it was much easier to talk about. It has been a very contentious issue. Broadly, the most vulnerable countries have called for mechanisms to address the fact that they are, and will continue to, experience loss and damage from climate change impacts like sea level rise and extreme weather. Those countries who have emitted the most fear this could lead to unlimited liability. When I first started working on it I’d often get a worried look when I mentioned the topic.

“In a side event during the first week at Sharm El Sheikh, I heard someone say “some magic has happened” and we can now talk about this in the mainstream. We also saw a series of announcements from countries committing finance for Loss and Damage. Then, finally, after two weeks of negotiations ran into extra time, countries agreed to establish a fund for Loss and Damage.

“This was a huge victory for the developing countries. Lots of questions remain about how it will work, who will pay into it, and who will benefit, but nevertheless it marks a big step. Developing countries (especially AOSIS, the Alliance of Small Island States) have been working on this for decades. The negotiators work so hard, often into the night, it’s incredible.

“My overall view is that COP continues to be a difficult process, but it is shifting, maybe substantially. Many view COP as a talk shop and suggest it’s a waste of time, but I disagree. Although the process is tortuous, slow, and frustrating, it is the best one we have, and still vital. Progress is way too slow but there is progress. Every country is represented, and we don’t have any other process on climate change where that is the case. The developing countries have power in numbers at the COP that I am not sure they have in any other forum on climate change.”

Dr Alix Dietzel (fourth from right on the back row) at COP27

Is 1.5C still alive?

Colin: “The International Energy Agency expects fossil fuel demand to peak as early as 2025. However, with all countries harbouring exploitable fossil fuel resources racing to extract them (with our former Secretary of State for Business, Energy and Industrial Strategy Rees-Mogg vowing in September 2022 to “squeeze every last drop of oil” out of the North Sea) and key initiatives such as the Glasgow Financial Alliance for Net Zero failing to deliver on their promises, fossil fuels will not be phased out anytime soon.

“At the same time, pinning our hopes on Carbon Capture and Storage (CCS) is misguided as current capacities amount to four hours of global emissions and International Energy Agency projections suggest that capacities in 2030 will amount to 16 hours of emissions. This implies that in the absence of a sustained global financial commitment towards demand reduction or sustainable supply, limiting average global temperature rise to 1.5 above will be very difficult indeed.”

Rachel: “A key goal in Glasgow and in Sharm El Sheikh has been to keep 1.5°C alive. Some countries were attempting to backslide on mitigation goals during the final days, but in the end 1.5°C remained in the text. It’s disappointing that we didn’t see an increase in ambition from Glasgow, but 1.5°C is still there – even if “on life support”, as noted by Alok Sharma.

“It’s easy for us to do an academic analysis and speculate as to whether or not we think 1.5°C is politically feasible. But the IPCC has spelled it out clearly: every fraction of a degree of warming matters. What’s important is that we increase ambition to reduce emissions, and we phase out fossil fuels, so that we can limit global warming as much as possible.”

———————————-

This blog is written by Cabot Institute for the Environment members Dr Alix Dietzel, Dr Colin Nolden, Dr Rachel James and Amanda Woodman-Hardy.

Arctic is warming nearly four times faster than the rest of the world – new research

Posted on August 16, 2022April 16, 2023 by janet.crompton

New research estimates that the Arctic may be warming four times faster than the rest of the world.
Netta Arobas/Shutterstock

The Earth is approximately 1.1℃ warmer than it was at the start of the industrial revolution. That warming has not been uniform, with some regions warming at a far greater pace. One such region is the Arctic.

A new study shows that the Arctic has warmed nearly four times faster than the rest of the world over the past 43 years. This means the Arctic is on average around 3℃ warmer than it was in 1980.

This is alarming, because the Arctic contains sensitive and delicately balanced climate components that, if pushed too hard, will respond with global consequences.

Why is the Arctic warming so much faster?

A large part of the explanation relates to sea ice. This is a thin layer (typically one metre to five metres thick) of sea water that freezes in winter and partially melts in the summer.

The sea ice is covered in a bright layer of snow which reflects around 85% of incoming solar radiation back out to space. The opposite occurs in the open ocean. As the darkest natural surface on the planet, the ocean absorbs 90% of solar radiation.

When covered with sea ice, the Arctic Ocean acts like a large reflective blanket, reducing the absorption of solar radiation. As the sea ice melts, absorption rates increase, resulting in a positive feedback loop where the rapid pace of ocean warming further amplifies sea ice melt, contributing to even faster ocean warming.

This feedback loop is largely responsible for what is known as Arctic amplification, and is the explanation for why the Arctic is warming so much more than the rest of the planet.

Blocks of melting sea ice revealing a deep blue sea. — Melting sea ice in the Arctic Ocean.
Nightman1965/Shutterstock

Is Arctic amplification underestimated?

Numerical climate models have been used to quantify the magnitude of Arctic amplification. They typically estimate the amplification ratio to be about 2.5, meaning the Arctic is warming 2.5 times faster than the global average. Based on the observational record of surface temperatures over the last 43 years, the new study estimates the Arctic amplification rate to be about four.

Rarely do the climate models obtain values as high that. This suggests the models may not fully capture the complete feedback loops responsible for Arctic amplification and may, as a consequence, underestimate future Arctic warming and the potential consequences that accompany that.

How concerned should we be?

Besides sea ice, the Arctic contains other climate components that are extremely sensitive to warming. If pushed too hard, they will also have global consequences.

One of those elements is permafrost, a (now not so) permanently frozen layer of the Earth’s surface. As temperatures rise across the Arctic, the active layer, the topmost layer of soil that thaws each summer, deepens. This, in turn, increases biological activity in the active layer resulting in the release of carbon into the atmosphere.

Arctic permafrost contains enough carbon to raise global mean temperatures by more than 3℃. Should permafrost thawing accelerate, there is the potential for a runaway positive feedback process, often referred to as the permafrost carbon time bomb. The release of previously stored carbon dioxide and methane will contribute to further Arctic warming, subsequently accelerating future permafrost thaw.

A second Arctic component vulnerable to temperature rise is the Greenland ice sheet. As the largest ice mass in the northern hemisphere, it contains enough frozen ice to raise global sea levels by 7.4 metres if melted completely.

A man and woman standing on the edge of a flooded coastal road. — The Greenland ice sheet contains enough frozen ice to raise global sea levels by 7.4 metres if completely melted.
MainlanderNZ/Shutterstock

When the amount of melting at the surface of an ice cap exceeds the rate of winter snow accumulation, it will lose mass faster than it gains any. When this threshold is exceeded, its surface lowers. This will quicken the pace of melting, because temperatures are higher at lower elevations.

This feedback loop is often called the small ice cap instability. Prior research puts the required temperature rise around Greenland for this threshold to be be passed at around 4.5℃ above pre-industrial levels. Given the exceptional pace of Arctic warming, passing this critical threshold is rapidly becoming likely.

Although there are some regional differences in the magnitude of Arctic amplification, the observed pace of Arctic warming is far higher than the models implied. This brings us perilously close to key climate thresholds that if passed will have global consequences. As anyone who works on these problems knows, what happens in the Arctic doesn’t stay in the Arctic.

——————————

This blog is written by Cabot Institute for the Environment member, Jonathan Bamber, Professor of Physical Geography, University of Bristol.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Wheel of Time is set thousands of years from now, yet it’s still burdened with today’s climate change

Posted on January 6, 2022March 29, 2023 by janet.crompton

The epic fantasy series has been turned into a tv show on Amazon.
JAN THIJS/AMAZON STUDIOS

Wheel of Time, the 14-book epic fantasy now turned into an Amazon Prime TV series, is a medieval-style adventure set in the Third Age of the World of the Wheel. While not explicit in the storyline, notes from the late author suggest that the First Age was actually modern-day Earth, which ended with a dramatic event (perhaps even climate change). From these notes, we estimate the show takes place around 18,000 years from today.

For climate scientists like us, this poses an interesting question: would today’s climate change still be experienced in the World of the Wheel, even after all those centuries?

About a quarter of carbon dioxide emitted today will remain in the atmosphere even 18,000 years from now. According to biogeochemistry models, carbon dioxide levels could be as high as 1,100 parts per million (ppm) at that point. That’s compared with a present-day value of 415ppm. This very high value assumes that the Paris climate goals will be exceeded and that many natural stores of carbon will also be released into the atmosphere (melting permafrost, for instance).

But the high carbon dioxide concentrations do not necessarily mean a warmer climate. That’s because, over such a long period, slow changes in the orbit and tilt of the planet become more important. This is known as the Milankovitch Cycle and each cycle lasts for around 100,000 years. Given that we are currently at the peak of such a cycle, the planet will naturally cool over the next 50,000 years and this is why scientists were once worried about a new ice age.

But will this be enough to offset the warming from the remaining carbon dioxide in the atmosphere? The image below shows a version of the classic warming stripes, a ubiquitous symbol of the past 150 years of climate change, but instead applied over 1 million years:

Annotated stripes — Warming stripes of Earth (and the World of the Wheel) for a million years. Today’s climate crisis will disrupt the Milankovitch cycle and its effects will last for many thousands of years.
Authors modified from Dan Lunt et al, Author provided

You can clearly see the 100,000 year Milankovitch cycles. Anything red can be considered anthropogenic climate change, and the events of the Wheel of Time are well within this period. Even the descending Milankovitch cycle won’t be enough to counteract the increased warming from carbon dioxide, and so the inhabitants of the World of the Wheel would still experience elevated temperatures from a climate crisis that occurred 18,000 years ago.

Simulating the weather of the World

However, some of the weather changes from the still-elevated temperatures could be offset by other factors. Those 18,000 years aren’t very long from a geological perspective, so in normal circumstances the landmasses would not change significantly. However, in this fantasy future magical channelers “broke” the world at the end of the Second Age, creating several new supercontinents.

To find out how the climate would work in the World of the Wheel, we used an exoplanet model. This complex computer program uses fundamental principles of physics to simulate the weather patterns on the hypothetical future planet, once we had fed in its topography based on hand-drawn maps of the world, and carbon dioxide levels of 830ppm based on one of the high potential future carbon pathways.

According to our model, the World of the Wheel would be warm all over the surface, with temperatures over land never being cold enough for snow apart from on the mountains. No chance of a white Christmas in this future. Here the story and the science diverge, as at times snow is mentioned in the Wheel of Time. The long-term effects of climate change may have surpassed the imagination of its author, the late great Robert Jordan.

An animated map with arrows — A simulation focused on where The Wheel of Time events take place, showing surface winds (white arrows).
climatearchive.org, Author provided

The World of the Wheel would have stronger and wavier high-altitude jet streams than modern-day Earth. This is likely because there are more mountain ranges in the World of the Wheel, which generate atmospheric waves called Rossby waves, causing oscillations in the jet. There is some limited evidence that the jet stream gets wavier with climate change as well, although this is likely to be less important than the mountain ranges. The jet would bring moisture from the western ocean on to land, and deposit it north of the Mountains of Dhoom. Surprising then, that this region (The Great Blight) is so desert-like in the books – perhaps there is some magic at play to explain this.

Our simulation of the World of the Wheel, showing the jet stream (red and yellow arrows), surface winds (white arrows) and cloud cover (white mist). Source: https://climatearchive.org/wot.

Winds would often revolve around two particularly enormous mountains, Dragonmount and Shayol Ghul, before blowing downslope and reaching far across the land masses. The peak of Dragonmount itself is nearly always surrounded by clouds, and this is because the mountain is so large the winds travelling up it force surface moisture to higher altitudes, thus cooling it, and forming clouds.

The fact winds would be so different from modern-day Earth is predominantly caused by topography, not the underlying increased temperatures from climate change. Nevertheless, in the World of the Wheel, it is clear that despite the extremely long time since carbon polluted the atmosphere, the inhabitants are still exposed to warmer than usual temperatures.

Acknowledging just how long the effects of climate change will persist for should be a catalyst for change. Yet, even after accepting the facts, we face psychological barriers to subsequent personal action, not least because comprehending the timescales of climate change requires a considerable degree of abstraction. But, given the known changes in extreme weather from climate change, and given how long these changes will remain, we must ask ourselves: how would the mysterious and powerful Aes Sedai stop the climate crisis?

—————————

This blog is by Caboteers Professor Dann Mitchell, Professor of Climate Science, University of Bristol; Emily Ball, PhD Candidate, Climate Science, University of Bristol; Sebastian Steinig, Research Associate in Paleoclimate Modelling, University of Bristol; and Rebecca Áilish Atkinson, Research Fellow, Cognitive Psychology, University of Sussex.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Beast from the East 2? What ‘sudden stratospheric warming’ involves and why it can cause freezing surface weather

Posted on February 9, 2021March 30, 2023 by janet.crompton

A “sudden stratospheric warming” event took place in early January 2021, according to the Met Office, the UK’s national weather service. These events are some of the most extreme of atmospheric phenomena, and I study them as part of my academic research. The stratosphere is the layer of the atmosphere from around 10km to 50km above the Earth’s surface, and sudden warming up there can lead to very cold weather over Europe and Siberia, with an increased possibility of snow storms.

Happy Major Sudden Stratospheric Warming day! pic.twitter.com/DYYelxYYsb

— Simon Lee (@SimonLeeWx) January 5, 2021

In winter the polar regions are in darkness 24 hours a day, and so the stratosphere over the north pole drops to -60℃ or even lower. The pole is surrounded by strong westerly winds, forming what is known as the polar vortex, a normal occurrence which develops every winter. However, about six times a decade, this vortex can break down in dramatic fashion. This can lead to temperatures over the pole increasing by up to 50°C over a few days, although temperatures are so low that they still remain below freezing. The average wind direction around the pole may also reverse, in which case a “sudden stratospheric warming” event has occurred.

The disturbance in the stratosphere can then be transmitted downward through the atmosphere. If this disturbance reaches the lower levels of the atmosphere it can affect the jet stream, a current of air which normally snakes eastwards around the planet, dividing colder polar air from warmer air to the south.

Where the jet stream crosses the Atlantic it usually points towards the British Isles, but sudden stratospheric warming can lead it to shift towards the equator. As air currents are temporarily rearranged, warmer Atlantic air is replaced by cold air from Siberia or the Arctic, and Europe and Northern Asia may experience unusually cold weather. This is what happened when the infamous “Beast from the East” passed through Europe in 2018, causing huge snowstorms and dozens of deaths.

It can take a number of weeks for the impact of stratospheric warming to reach the surface, or the process may only take a few days. These events are hard to predict in advance. Some can only be predicted a few days ahead while others may be forecast from around two weeks before.

A number of factors including a La Niña event in the tropical Pacific contributed to a strong vortex in early winter 2020/21. Strong vortices are hard to shift, meaning a sudden stratospheric warming event was not looking particularly likely. However, from just before Christmas, weather forecast model predictions began to converge on a likely stratospheric warming event in early January.

From stratosphere to surface

Around two thirds of stratospheric warming events have a detectable surface impact, up to 40 days after the onset of the event. This is usually marked by lower than normal temperatures across Northern Europe and Asia, extending into western Europe, but with warmer temperatures over the eastern Canadian Arctic.

It’s not yet clear why some stratospheric warming events take weeks to impact the surface while others are felt days later, but it may be related to how the polar vortex changes around the onset of a warming event. The vortex can split into two smaller “child vortices”, or it can be displaced from its more usual position centred near the pole, to being over northern Siberia.

Early indications suggested that 2021’s event was more likely to be split, but it subsequently showed more features of a displacement. It is not unusual for the vortex to show such mixed signals.

Colleagues and I recently developed a new method for tracking the impact of a warming event from its onset in the stratosphere to when its effect reaches the surface. We analysed 40 such events from the past 60 years, to try and figure out when we might expect extreme surface weather.

Most importantly, we found that warming events in which the stratospheric polar vortex splits in two generally lead to surface impacts appearing faster and stronger. So although there is an increased chance of snow and extreme cold in mid to late January 2021, other confounding factors may act to reduce this impact.

There are always competing forces at work in the atmosphere. Few people noticed the sudden stratospheric warming of January 2019 for example, which had little impact on the European winter. In that instance, there was a westerly influence on the North Atlantic winds, which originated in the tropics. This may have acted to oppose any stratospheric effect favouring easterly winds. In 2021, the battle is between the stratospheric warming and La Niña.

Sudden stratospheric warming events are a natural atmospheric fluctuation, not caused by climate change. So even with climate change, these events will still occur, which means that we need to be adaptable to an even more extreme range of temperatures.

———————————

This blog is written by Cabot Institute member Dr Richard Hall, Research Associate, Climate Dynamics Group, University of Bristol. This article is republished from The Conversation under a Creative Commons license. Read the original article.

Dr Richard Hall

We have the vaccine for climate disinformation – let’s use it

Posted on February 4, 2020March 31, 2023 by janet.crompton

Exposing people to likely disinformation campaigns about bushfire causes will help inoculate them. JASON O’BRIEN/AAP

Australia’s recent bushfire crisis will be remembered for many things – not least, the tragic loss of life, property and landscape. But one other factor made it remarkable: the deluge of disinformation spread by climate deniers.

As climate change worsens – and with it, the bushfire risk – it’s well worth considering how to protect the public against disinformation campaigns in future fire seasons.

So how do we persuade people not to be fooled? One promising answer lies in a branch of psychology called “inoculation theory”. The logic is analogous to the way a medical vaccine works: you can prevent a virus spreading by giving lots of people a small dose.

In the case of bushfire disinformation, this means exposing, ahead of time, the myths most likely to be perpetrated by sceptics.

Bushfire bunkum

Disinformation can take many forms, including cherry-picking or distorting data, questioning of the scientific consensus by presenting fake experts, and outright fabrication.

On the issue of bushfires in Australia, there is little scientific doubt that human-caused climate change is increasing their magnitude and frequency. But spurious claims on social media and elsewhere of late sought to muddy the waters:

bots and trolls disseminated false arson claims which downplayed the impact of climate change on the bushfires
NewsCorp reported more than 180 arsonists had been arrested “in the past few months”. The figure was a gross exaggeration and distorted the real numbers
The misleading arson claim went viral after Donald Trump Jr, the president’s son, tweeted it. A UK government minister, Heather Wheeler, also repeated the false claim in the House of Commons
NSW Nationals leader John Barilaro, among others, wrongly suggested a lack of hazard reduction burning – the fault of the Greens – had caused the fires
Conservative commentators claimed the 2019-20 bushfires were no worse than those of the past.

Where will it go next?

Climate science clearly indicates Australia faces more dangerous fire weather conditions in the future. Despite this, organised climate denial will inevitably continue.

Research has repeatedly shown that if the public knows, ahead of time, what disinformation they are likely to encounter and why it is wrong, they are less likely to accept it as true.

This inoculation involves two elements: an explicit warning of an impending
attempt to misinform, and a refutation of the anticipated disinformation.

For example, research has shown that if people were told how the tobacco industry used fake experts to mislead the public about the health risks of smoking, they were less likely to be misled by similar strategies used to deny climate change.

It is therefore important to anticipate the next stage of disinformation about the causes of bushfire disasters. One likely strategy will be to confuse the public by exploiting the role of natural climate variability.

This tactic has been used before. When natural variability slowed global warming in the early 2000s, some falsely claimed that global warming “had stopped”.

Of course, the warming never stopped – an unexceptional natural fluctuation merely slowed the process, which subsequently resumed.

Natural climate variability may bring the occasional mild fire season in future. So let’s arm ourselves with the facts to combat the inevitable attempts to mislead.

Here are the facts

The link between human-caused climate change and extreme weather conditions is well established. But natural variability, such as El Niño and La Niña events in the Pacific Ocean may at times overshadow global warming for a few years.

The below video illustrates this. We used historical data from Adelaide to project the expected incidence of extreme heatwaves for the rest of the century, assuming a continued warming trend of 0.3℃ per decade.

The top panel shows the distribution of all 365 daily maximum temperatures for a year, with the annual average represented by the vertical red line. As the years tick over, this distribution is moving up slowly; the red line increasingly diverges from the average temperature observed before the climate started changing (the vertical black line).

The bottom panel shows the expected incidence of extreme heatwaves for each year until 2100. Each vertical line represents an intense heatwave (five consecutive days in excess of 35℃ or three days in excess of 40℃). Each heatwave amplifies the fire danger in that year.

The analysis in the video clarifies several important aspects of climate change:

the number and frequency of extreme heatwaves will increase as the climate continues to warm
for the next few decades at least, years with heatwaves may be followed by one or more years without one
the respite will only be brief because the inexorable global warming trend makes extreme fire conditions more and more inevitable.

Looking ahead

When it comes to monster bushfire seasons, the link to climate change is undeniable. This season’s inferno is a sign of worse to come – even if it doesn’t happen every year.

Educating the public on climate science, and the tactics used by disinformers, increases the chance that “alternative facts” do not gain traction.

Hopefully, this will banish disinformation to the background of public debate, paving the way for meaningful policy solutions.

———————————————
This blog is written by Cabot Institute member Professor Stephan Lewandowsky, Chair of Cognitive Psychology, University of Bristol and John Hunter, University Associate, Institute for Marine and Antarctic Studies, University of Tasmania. This article is republished from The Conversation under a Creative Commons license. Read the original article.

Global warming ‘hiatus’ is the climate change myth that refuses to die

Posted on May 20, 2019April 13, 2023 by janet.crompton

File 20181210 76977 hkxl6p.jpg?ixlib=rb 1.1 — riphoto3 / shutterstock

The record-breaking, El Niño-driven global temperatures of 2016 have given climate change deniers a new trope. Why, they ask, hasn’t it since got even hotter?

In response to a recent US government report on the impact of climate change, a spokesperson for the science-denying American Enterprise Institute think-tank claimed that “we just had […] the biggest drop in global temperatures that we have had since the 1980s, the biggest in the last 100 years.”

These claims are blatantly false: the past two years were two of the three hottest on record, and the drop in temperature from 2016 to 2018 was less than, say, the drop from 1998 (a previous record hot year) to 2000. But, more importantly, these claims use the same kind of misdirection as was used a few years ago about a supposed “pause” in warming lasting from roughly 1998 to 2013.

At the time, the alleged pause was cited by many people sceptical about the science of climate change as a reason not to act to reduce greenhouse pollution. US senator and former presidential candidate Ted Cruz frequently argued that this lack of warming undermined dire predictions by scientists about where we’re heading.

However, drawing conclusions on short-term trends is ill-advised because what matters to climate change is the decade-to-decade increase in temperatures rather than fluctuations in warming rate over a few years. Indeed, if short periods were suitable for drawing strong conclusions, climate scientists should perhaps now be talking about a “surge” in global warming since 2011, as shown in this figure:

Global temperature observations compared to climate models. Climate-disrupting volcanoes are shown at the bottom, and the purported hiatus period is shaded. 2018 values based on year to date (YTD).
NASA; Berkeley Earth; various climate models., Author provided

The “pause” or “hiatus” in warming of the early 21st century is not just a talking point of think-tanks with radical political agendas. It also features in the scientific literature, including in the most recent report of the Intergovernmental Panel on Climate Change and more than 200 peer-reviewed articles.

Research we recently published in Environmental Research Letters addresses two questions about the putative “pause”: first, is there compelling evidence in the temperature data alone of something unusual happening at the start of the 21st century? Second, did the rise in temperature lag behind projections by climate models?

In both cases the answer is “no”, but the reasons are interesting.

Reconstructing a historical temperature record from instruments designed for other purposes, such as weather forecasting, is not always easy. Several problems have affected temperature estimates for the period since 2000. The first of these was the fact that uneven geographical distribution of weather stations can influence the apparent rate of warming. Other factors include changes in the instruments used to measure ocean temperatures. Most of these factors were known at the time and reported in the scientific literature, but because the magnitudes of the effects were unknown, users of temperature data (from science journalists to IPCC authors) were in a bind when interpreting their results.

‘This glacier was here in 1908’: warming might fluctuate, but the long-term trend is clear.
Matty Symons/Shutterstock

A more subtle problem arises when we ask whether a fluctuation in the rate of warming is a new phenomena, rather than the kind of variation we expect due to natural fluctuations of the climate system. Different statistical tests are needed to determine whether a phenomena is interesting depending on how the data are chosen. In a nutshell, if you select data based on them being unusual in the first place, then any statistical tests that seemingly confirm their unusual nature give the wrong answer. (The statistical issue here is similar to the fascinating but counterintuitive “Monty Hall problem”, which has caught out many mathematicians).

When the statistical test is applied correctly, the apparent slowdown in warming is no more significant than other fluctuations in the rate of warming over the past 40 years. In other words, there is no compelling evidence that the supposed “pause” period is different from other previous periods. Neither is the deviation between the observations and climate model projections larger than would be expected.

That’s not to say that such “wiggles” in the temperature record are uninteresting – several of our team are involved in further studies of these fluctuations, and the study of the “pause” has yielded interesting new insights into the climate system – for example, the role of changes in the Atlantic and Pacific oceans.

There are lessons here for the media, for the public, and for scientists.

For scientists, there are two lessons: first, when you get to know a dataset by using it repeatedly in your work, make sure you also still remember the limitations you read about when first downloading it. Second, remember that your statistical choices are always part of a cascade of decisions, and at least occasionally those decisions must be revisited.

For the public and the media, the lesson is to check claims about the data. In particular, when claims are made based on short periods or specific datasets, they are often designed to mislead. If someone claims the world hasn’t warmed since 1998 or 2016, ask them why those specific years – why not 1997 or 2014? Why have such short limits at all? And also check how reliable similar claims have been in the past.

The technique of misinformation is nicely described in a quote attributed to climate researcher Michael Tobis:

“If a large data set speaks convincingly against you, find a smaller and noisier one that you can huffily cite.”

Global warming didn’t stop in 1998. Don’t be fooled by claims that it stopped in 2016 either. There is only one thing that will stop global warming: cuts to greenhouse gas emissions.

———————————
This blog is written by Kevin Cowtan, Professor of Chemistry, University of York and Professor Stephan Lewandowsky, Chair of Cognitive Psychology, University of Bristol Cabot Institute. This article is republished from The Conversation under a Creative Commons license. Read the original article.

Kevin Cowtan

Stephan Lewandowsky

Courts can play a pivotal role in combating climate change

Posted on November 12, 2018April 3, 2023 by janet.crompton

Calin Tatu/Shuttestock.com

The international community has widely acknowledged the severe threats posed by the impacts of climate change to a series of human rights, including the rights to life, health, and an adequate standard of living. But a stark gap has emerged between this acknowledgement in global climate policy – evidenced by a non-binding clause in the preamble of the Paris Agreement – and their actions to meet promised targets.

How can we hold governments accountable to their human rights duties? A Dutch case recently upheld by the appeals court might hold the answer.

In June 2015, The Hague District Court and a group of 886 concerned citizens, united by the environmental interest group Urgenda Foundation, made history. This, the first successful climate change case brought on human rights and civil law grounds, saw the Dutch government ordered to reduce their greenhouse gas emissions by a minimum of 25% on 1990 levels by the year 2020.

Three years on – against a backdrop of intense scrutiny and after an appeal lodged by the government – The Hague Court of Appeal upheld this decision on October 9. Indeed, it has gone significantly further in affirming the duties of care owed by the state to its people. The court considered the weight of the scientific evidence presented by the Intergovernmental Panel on Climate Change (IPCC) and the recommendations of successive UN conferences to reach an informed conclusion on the required mitigation targets commensurate with the prevention of dangerous climate change.

Marjan Minnesma, director of environmental group Urgenda, arrives at court prior to the appeal. Jerry Lampden/EPA

Significantly, the judges reached this decision by applying the European Convention on Human Rights: the right to private and family life and the right to life more broadly. As such, this case reaffirms the existence of obligations on the part of the state to take concrete measures to prevent the infringement of these rights where the authorities are aware of the existence of a real and imminent threat.

These obligations were held to extend to industrial activities which threaten the rights of people within the state’s jurisdiction. Based on an analysis of the scientific evidence, the court concluded that climate change presents a real and imminent threat to the enjoyment of citizens’ rights as spelled out in the EU convention. They ruled that a 25% emissions reduction is the minimum required to fulfil the government’s duty of care.

Human rights alarm

The Urgenda appeal decision was handed down too early for the findings of the most recent IPCC report on global warming of 1.5ºC, which was published the day before the ruling, to be integrated into the judges’ reasoning. But these findings will significantly strengthen the evidential basis of future claims.

The IPCC report outlines the stark increase in the risks to human health, food and water security, and livelihoods associated with 2ºC of warming, when compared to 1.5ºC. The evidence presented on human health, including the increased risk of heat-related morbidity and mortality, projected with “very high confidence”, is particularly striking. The climate is currently 1ºC warmer than pre-industrial levels, and with the planet projected to reach 1.5ºC as early as 2030 if current trends continue, the alarm on the imminence of the threat to human rights has been sounded.

No legally binding human rights provisions or remedies are provided within the international climate change regime. And so we must turn to the courts to clarify state duties. The Urgenda case sets an encouraging precedent. And there are many more examples of rights-based claims being brought against governments in Belgium, Canada, Colombia, the UK, and even against the EU institutions. This marks a sea change in the use of human rights to hold policymakers to account for their inaction on climate change.

The decision by the Netherlands court of appeals in #Urgenda immediately becomes the most important judicial decision yet on the application of human rights law to climate change. 1/10 https://t.co/8ioKxFEjly

— John H Knox (@JohnHKnox) 9 October 2018

A new approach

In the face of the severity and imminence of the environmental risks we face, the approach to human rights protection adopted by the Urgenda judges is crucial. If courts focus on the imminent risks to human life and health, cases brought forward by particularly climate-vulnerable groups should be prioritised.

Individuals most at risk from rising temperatures and extreme weather events – including those whose livelihoods, socio-economic status, and geographic susceptibility result in them being disproportionately affected – would have the strongest claims. Civil society organisations have a crucial role to play in facilitating access to justice for such individuals, for whom entrenched structural barriers often mean that individual access to the courts remains out of reach.

To effectively accommodate climate risks of this nature the existing legal doctrine will need to be adapted, bringing together environmental principles and human rights. The role of the courts themselves is being called into question by climate litigation: the separation of powers between policymakers and the judiciary is embedded in legal systems around the globe, yet the protection of fundamental rights is intended to transcend this divide. It is the duty of the courts to act as a check on executive action and, in this case, inaction, where the enjoyment of rights is in jeopardy.

Never before has the role of the courts been so significant in influencing the path of global policy. In the face of inadequately ambitious action by policy-makers, civil society movements and the courts are the agents of change securing climate action.

——————————————-
This blog was written by Cabot Institute member Alice Venn, a PhD Candidate in Environment, Energy & Resilience and Unit Coordinator in Environmental Law, University of Bristol. This article is republished from The Conversation under a Creative Commons license. Read the original article.

Alice Venn

The Paris Agreement – where are we now?

Posted on October 23, 2018April 4, 2023 by janet.crompton

This year the Cabot Institute Annual Lecture posed a critical question: where are we with current efforts to tackle global climate change? The event brought together over 800 people to hear from leading Cabot Institute experts in climate science, policy, and justice, Dr Jo House, Dr Dann Mitchell, Dr Alix Dietzel and Professor Tony Payne. It was both an appraisal of the findings of the recently published report of the Intergovernmental Panel on Climate Change (IPCC), and a grounded call to climate action.

Paris commitments

In 2015 world leaders adopted the Paris Agreement committing all parties to limiting global average temperatures to well below 2 °C above pre-industrial levels and to pursue efforts to limit warming to 1.5 °C. All countries undertook to achieve global peaking of greenhouse gas emissions as soon as possible and to enact increasingly ambitious mitigation measures in line with the overarching temperature goals. The Paris Agreement, in contrast to the preceding Kyoto Protocol, is not based on legally binding reductions targets for developed countries, but on a voluntary system of pledges known as ‘nationally determined contributions’ for all parties which will be subject to a stocktake of global progress every five years, beginning in 2023.

Although the Paris Agreement initially offered great promise with pledges being made by both developed and developing countries, a report by the UN Environment Programme in November 2017 examining progress towards the global temperature goals found that even if all current pledges are honoured, we remain on track for some 3 °C of warming by 2100. In light of this, and under the Presidency of Fiji, the first Small Island State to preside over a Conference of the Parties at COP23 last year, the focus has been on building momentum for more urgent action through the facilitative ‘Talanoa dialogue’ and on hashing out the final operating procedures for the Agreement. The findings of the IPCC Report on Global Warming of 1.5°C, published on 8 October represent a further important piece of the picture of global progress, which three of the Cabot speakers shed light upon as contributing authors.

Why 0.5°C of warming matters

The findings of the report are significant in illustrating the projected differences in climate change impacts between the 1.5°C and 2°C temperature thresholds. Dr Dann Mitchell outlined the evidence for increases in regional mean temperatures and for the increasing likelihood of temperature extremes of the kind witnessed during this summer’s European heatwave, which we could see occur almost every year at 2°C of warming. These extremes, together with the projected intensification of storms presented in the report, are closely linked to human risks to health, wellbeing and livelihoods.

Dr Dann Mitchell

Professor Tony Payne echoed these concerns with respect to the findings of the report on sea-level rise which predict an extra 10cm rise between the 1.5°C and 2°C temperature thresholds, equating, in turn, to an additional 10 million people at risk of related impacts including inundation and displacement. The destabilisation of the ice sheets is set to become more likely beyond 1.5°C, entailing risks of much greater sea-level rise in the future. Professor Payne further outlined the strikingly severe consequences for coral reefs of the two temperature thresholds, with projections that at 2°C all coral in the oceans will die, while by limiting temperature to 1.5°C, some 10-30% of coral will survive. Reefs are not only crucial for the maintenance of healthy marine ecosystems, but also for the millions of people around the world who depend upon those ecosystems for their food security and livelihoods.

Professor Tony Payne

A call for action

Against these stark warnings on the significance of limiting global temperatures to 1.5°C, Dr Jo House outlined some key recommendations for how we can get on track. The IPCC report sets out a number of pathways for action, each calling for changes across a broad spectrum of policy sectors with the aim of rapidly reducing greenhouse gas emissions and enhancing the absorption of existing carbon in the atmosphere. These changes include moving away from fossil fuels to renewable sources of energy, greening the transport sector, replanting forests, and investing in carbon capture and storage technologies. Dr House underlined the importance of action at all levels of governance to meet these goals. At the national level in the UK under the provisions of the Climate Change Act we are already committed to an 80% reduction on 1990 levels by 2050, while at the city level in Bristol, the Climate and Energy Security Framework commits to the same target, with a 50% reduction to be achieved by 2025.

Dr Jo House

This action in climate policy is increasingly being driven by sub-state actors and Dr Alix Dietzel highlighted the crucial role that local government, civil society groups, citizens initiatives, corporations, and individuals are playing in this. Dr Dietzel expressed cause for hope in the reaction of sub-state actors to the announcement of the withdrawal of the United States from the Paris Agreement, with the ‘WE ARE STILL IN’ movement garnering support from city mayors, governors, tribal leaders, universities, and businesses for continuing commitment to the Paris goals. At the individual level, the actions we can all take within the boundaries of our own capabilities were discussed, outlining our capacity to affect change through our consumption and lifestyle choices. The need to consider the ethical questions surrounding our responsibilities as individuals and global citizens remains crucial, particularly in light of the disproportionately harmful effects that climate impacts will have upon those who have contributed least to the problem.

Dr Alix Dietzel

The risks of inaction on the 1.5°C threshold were balanced against the opportunities and benefits of action by the panel. The successful lobbying efforts of climate-vulnerable states to embed the 1.5°C threshold within the Paris framework, alongside the commitment of many governments and sub-state actors to meet it, are cause for hope but we still have a long way to go.

——————————
This blog was written by Cabot Institute member Alice Venn, a PhD Candidate in Environment, Energy & Resilience at the University of Bristol’s Law School.

Alice Venn

Listen again to the Annual Lecture
View the presentation slides
View the photos on Flickr
View our Moments or check out #CabotLecture2018 on Twitter.

Monitoring greenhouse gas emissions: Now more important than ever?

Posted on October 15, 2018April 13, 2023 by janet.crompton

As part of Green Great Britain Week, supported by BEIS, we are posting a series of blogs throughout the week highlighting what work is going on at the University of Bristol’s Cabot Institute for the Environment to help provide up to date climate science, technology and solutions for government and industry. We will also be highlighting some of the big sustainability actions happening across the University and local community in order to do our part to mitigate the negative effects of global warming. Today our blog will look at ‘Explaining the latest science on climate change’.

The IPCC report

On 8 October 2018 the Intergovernmental Panel on Climate Change (IPCC) [1] published their special report on Global Warming of 1.5 ˚C. As little as 24 hours after the report had been published, the results of the report were already receiving extensive global coverage in the media, with BBC News describing the report as the “final call”. The BBC News article also explicitly mentions that this is “the most extensive warning yet on the risks of rising global temperatures. Their dramatic report on keeping that rise under 1.5 ˚C states that the world is now completely off track, heading instead towards 3 ˚C. Staying below 1.5 ˚C will require ‘rapid, far-reaching and unprecedented changes in all aspects of society’ [2].”

Reading the report has quite honestly been somewhat overwhelming but also necessary to understand exactly what we are in for. And as much as I understand the difficulty one might face either with the technical terms of the report or even the volume of information, I would really encourage you to give it a read. This special report covers a wide range of subjects from oceans, ice and flooding to crops, health and economy. However, if you do find that the chapters themselves are too lengthy or difficult, there is an amazing interactive, and very easy way that will help you explore the impacts of a 1.5 ˚C, 2 ˚C and beyond on Carbon Brief’s website.

There are two distinct parts in the IPCC special report. The full technical report that consists of 5 chapters and a short summary for policy makers (SPM). The SPM clearly states that “Estimated anthropogenic global warming matches the level of observed warming to within ±20 %” which translates into ‘almost 100 % of the warming is the result of human activity’ [3] [4].

We know for a fact that human activity is warming the planet

One outcome of this “human activity” that we often discuss is the emission of greenhouse gases (GHGs). Through various types of activities, whether that is agriculture, deforestation or burning fossil fuels, GHGs are emitted to the atmosphere. Without going too much into the chemistry and physics, what these GHGs do is change the mixing ratios within the atmosphere, resulting in greater absorbance of infrared radiation. And it is this change in the composition of our atmosphere that we refer to as the manmade greenhouse gas effect which also leads to the warming described in the IPCC report. But far more than the warming effect itself, global warming has all sorts of impacts most of which you can explore through the interactive link above.

Greenhouse gases and a long history of monitoring

Some of the ‘usual suspects’ in the discussion of GHG emissions are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) (often described as the ‘major’ greenhouse gases [5]). However, an often-overlooked set of halogenated greenhouse gases are playing an increasingly large role in anthropogenic driven climate change. Gases like perfluorocarbons (PFCs) and hydrofluorocarbons (HFCs) are compounds that are emitted through some form of human activity. In the case of PFCs for example, the GHGs CF4 and C2F6 are two of the most volatile and long-lived gases monitored under the Kyoto protocol [6] and they are both primarily emitted through or during industrial processes. In contrast, HFCs are used widely as coolants in refrigerators and air-conditioning units, as blowing agents in foam manufacture and propellants in aerosols. They were originally introduced to replace ozone-depleting gases such as chlorofluorocarbons (CFCs), but like their predecessors, are potent greenhouse gases. Given the long lifetime of many of these halogenated gases, current emissions will influence the climate system for decades to come.

In order to monitor the accumulation of these gases in atmosphere, high-precision measurements are required. Through projects such as the Advanced Global Atmospheric Gases Experiment (AGAGE) [7] (figure 1 [8]) that has been measuring the composition of the global atmosphere continuously since 1978 and the National Oceanic and Atmospheric Administration’s Earth System Research Laboratory Global Monitoring Division, scientists have tracked the atmospheric concentrations of climate forcing gases from as far back as 1950s [9].

Figure 1: The AGAGE network

The Atmospheric Chemistry Research Group (ACRG) Chemistry Department, University of Bristol

The ACRG carries out research in the UK and worldwide in collaboration with other atmospheric chemistry research centres, universities and third parties. In the UK, the ACRG runs the UK Deriving Emissions linked to Climate Change network (DECC) [10], funded by the Department for Business, Energy and Industrial Strategy (BEIS) to measure atmospheric GHG and ozone depleting substances over the UK. These measurements are used in elaborate mathematical models to create top-down emission estimates for the UK and verify the UK GHG inventories submitted to the United Nations Framework Convention for Climate Change (UNFCCC) as part of the Kyoto protocol. Worldwide, the group is involved in the AGAGE network, monitoring global background levels of a wide range of GHGs. The ACRG runs 2 of the 9 global background stations under the AGAGE programme. One of these is the Mace Head station (Figure 2) on the west coast of Ireland, which is ideally placed for resolving northern hemispheric baseline air amongst European pollution events. The other AGAGE research station managed by the ACRG is the site at Ragged Point, Barbados. This site just north of the tropics, sits on the eastern edge of the island of Barbados and is directly exposed to the Atlantic. The researchers in ACRG study a variety of GHGs and a very large range of topics from maintaining instrument suites to ensuring the quality of the resulting data so that it can be used in modelling studies.

Figure 2: The Mace Head Station (Credit: Dr Kieran Stanley)

Why are measuring stations and networks like AGAGE so valuable and more important than ever?

The answer to this question is straightforward. Without measurement stations and their underlying networks, we would have very few means [11] by which to measure the accumulation of GHGs in the global atmosphere, and consequently no way of evaluating their emissions without relying on statistics from the industries that emit them. The current IPCC report is underpinned by such measurements, which allow scientists to estimate the impact of anthropogenic activity on past, present and future climates.

From Mauna Loa and its 60 -year record of atmospheric CO2 [12], to unexpected growth in emissions of banned substances such as CFC – 11 [13] and monitoring the accumulation of extremely long-lived greenhouse gases in the global atmosphere, atmospheric measurements stations have been our inside man when it comes to keeping track of what is happening in our atmosphere and to what extent human activities are altering its composition.

Perhaps now more than ever, in the light of the IPCC report, we can appreciate the importance of the data that have been collected over decades but also, the efforts of those who have been directly or indirectly involved in this kind of work. Continuing and expanding the measurement networks for these gases is and will be even more vital for a continued understanding of global and regional GHG emission trends.

References

[1] http://www.ipcc.ch/
[2] https://www.bbc.co.uk/news/science-environment-45775309
[3] http://report.ipcc.ch/sr15/pdf/sr15_spm_final.pdf
[4] https://www.carbonbrief.org/analysis-why-scientists-think-100-of-global-warming-is-due-to-humans
[5] https://www.c2es.org/content/main-greenhouse-gases/
[6] https://www.atmos-chem-phys.net/10/5145/2010/acp-10-5145-2010.pdf
[7] https://agage.mit.edu/
[8] https://agage.mit.edu/
[9] https://www.esrl.noaa.gov/gmd/about/aboutgmd.html
[10] http://www.bristol.ac.uk/chemistry/research/acrg/current/decc.html
[11] https://www.co2.earth/co2-ice-core-data
[12] https://www.co2.earth/daily-co2
[13] https://www.theguardian.com/environment/2018/may/16/mysterious-rise-in-banned-ozone-destroying-chemical-shocks-scientists

—————————-
This blog is written by Cabot Institute members Eleni Michalopoulou, Dr Dan Say, Dr Kieran Stanley and Professor Simon O’Doherty from the University of Bristol’s School of Chemistry.

Dan Say

Eleni Michalopoulou

Read other blogs in this Green Great Britain Week series:
1. Just the tip of the iceberg: Climate research at the Bristol Glaciology Centre
2. Monitoring greenhouse gas emissions: Now more important than ever?
3. Digital future of renewable energy
4. The new carbon economy – transforming waste into a resource
5. Systems thinking: 5 ways to be a more sustainable university
6. Local students + local communities = action on the local environment

Tag: global warming