Thoughts on passing 400 ppm

In the next few days, the Mauna Loa atmospheric CO2 record will pass 400 ppm. This isn’t the first time that’s happened – we first crossed the 400 ppm threshold in May 2013, but the annual, saw-tooth variation in levels as the Northern hemisphere boreal forest breathes in and out has dipped us below 400 a couple of times since. This crossing is likely to be special however, as it is probably going to be the last time anybody alive today will experience an atmosphere with LESS than 400 ppm CO2.

Human emissions have been pushing up atmospheric levels by about 2.2 ppm every year in recent years, so normally we would expect the annual monthly minimum to increase to beyond 400 ppm from this year’s September minimum of 397.1 ppm, however we are in the midst of one of the largest El Nino years for over a decade, and the drought in the tropics during El Nino years slow the growth of trees relative to normal years, and increases fires. Previous strong El Nino years (like 1997) have helped to push the annual CO2 increase to a massive 3.7 ppm, and this year’s strong El Nino, coupled with increased forest burning in Indonesia, along with fossil fuel burning, have led Ralph Keeling to predict the annual rise could be as much as 4.4 ppm this year.

So why does it matter? 400 is in truth a fairly arbitrary value to get excited about, a neat quirk of our counting system and no more important as a value to the atmosphere than your car odometer ticking from 99,999 to 100,000. It doesn’t mean the car is going to collapse, but it certainly catches your attention. It’s the same with the atmosphere – it gives us pause to consider what we’ve done, and what it might mean for the climate system. For me, the most outrageous thing is that we, an insignificant population of carbon based life forms, have managed to alter the chemical composition of the atmosphere! And not just by a little – by a lot! And let’s not forget that the atmosphere is big – really big!

To me, as an Earth Scientist that leads me to think about when in Earth history the planet has experienced such high levels of CO2 before. Measuring atmospheric CO2 in the geological past is tricky – for the past  ~800 thousand years we have a fantastic archive of trapped atmospheric gas bubbles in ice cores, and for the whole of that record CO2 never peaked above 300 ppm. Beyond the time for which we have the ice cores, we rely on geochemical proxies in marine and terrestrial sediments to estimate CO2 and that is the heart of my research. In a paper we published last year we showed that we have to go back to more than 2.3 Million years ago, to the very earliest Pleistocene and Pliocene to find atmospheric CO2 levels as high as we are about to permanently experience. What does that mean? Well the Pliocene was a similar world to today – the continents were in much the same place, the vegetation mix across this Earth was the same, except global temperatures were 2-3 degrees C higher than now, driven primarily by those high levels of CO2.

Another thing that strikes me today is how rapidly we’ve managed to change the atmosphere. In a little over 150 years since we started to burn fossil fuels with alacrity, we’ve gone from 280 ppm to 400 ppm. It’s hard to find geological records with the temporal precision to see changes that quick, but for sure we don’t know any time in Earth history when CO2 has changed so much, so quickly.

With COP21 in Paris just around the corner, perhaps saying goodbye to sub 400 ppm will focus minds to come up with a solution. I don’t know whether it will, or what a global solution would look like, but I hope beyond anything that we don’t do nothing.
Cabot Institute member Dr Marcus Badger is a Research Associate in the Organic Geochemistry Group in the School of Chemistry. His research involves using biomolecules and climate models to better understand the Earth system.

Why the Pliocene period is important in the upcoming IPCC report

Critical to our understanding of the Earth system, especially in order to predict future anthropogenic climate change, is a full comprehension of how the Earth reacts to higher atmospheric CO2 conditions. One of the best ways to look at what the Earth was like under higher CO2 is to look at times in Earth history when atmospheric CO2 was naturally higher than it is today. The perfect period of geological history is the Pliocene, which spans from 5.3 – 2.6 million years ago. During this time we have good evidence that the Earth was 2-3 degrees warmer than today, but other things, such as the position of the continents and the distribution of plants over the surface, was very similar to today.

There is therefore a significant community of oceanographers and climate modellers studying the Pliocene, many of whom were in Bristol last week for the 2nd Workshop on Pliocene climate, and one of the main points of discussion was the exact value of CO2 for the Pliocene.

80 top scientists from 12 countries gathered for the 2nd Workshop on Pliocene climate on 9-10 September 2013 at the University of Bristol

The imminent release of the first volume of the 5th assessments of the IPCC is also expected to include sections on Pliocene climate.

Today we published a paper in Philosophical Transactions of the Royal Society A which therefore represents an important contribution to the debate. Several records of Pliocene CO2 do exist, but their low temporal resolution makes interpretation difficult. There has also been some controversy about what these records mean, as some show surprisingly high variability, given what we understand about Pliocene climate.

We sampled a deep ocean core taken by the Ocean Drilling Program in the Carribean Sea. Cores such as this record the ancient envrionment as sediment collects over time like the progressive pages in a book, and by analysing the chemical composition of the layers a history of the Earth System can be discovered. The approach that Badger et al take is to use the carbon isotopic fractionation of photosynthetic algae, which has been shown to vary with atmospheric CO2.

What this study revealed is that atmospheric CO2 was actually quite low, at around 300 ppm for much of the warm period. What was also revealed was that CO2 was relatively stable, in contrast to previous work. This implies that in the Pliocene the Earth must have been quite sensitive to CO2, as small changes in atmospheric CO2 drove changes in climate. The study of Badger et al doesn’t explicitly reconstruct climate sensitivity but it does have important implications for future change.

The paper is published in a special volume of Philosophical Transactions of the Royal Society A, edited by Bristol scientists Dan Lunt, Rich Pancost, Andy Ridgewell and Harry Elderfield of Cambridge University. The volume is the result of the Warm Climates of the Past – A lesson for the Future? meeting which took place at the Royal Society in October 2011. The volume can be accessed here:

Marcus Badger

Chasing Ice with the All Party Parliamentary Climate Change Group

Watching the film of a self-confessed reformed climate skeptic with members of parliament and Lords isn’t how I usually spend my Tuesday morning, but it was what I found myself doing last Tuesday. The occasion for this unlikely meeting was a special screening of photographer James Balog’s film Chasing Ice for the All Party Parliamentary Climate Change Group (APPCCG), of which the Cabot Institute is a member. The film, which documents the work of the photographer’s Extreme Ice Survey, follows James and his team on a journey to record the retreat of 13 glaciers across the globe continuously over a two year period. 

I won’t spoil the film too much (and strongly encourage you to see it if you can) but suffice to say placing 28 cameras at locations across the globe in some of the most difficult terrains and extremes of temperature is a challenge for both the men and technology involved. The aim to take one photo every hour of daylight for two years solid was massively ambitious, but worth the effort and the pain, as the result is a spectacular demonstration of how our hydrocarbon based economy is changing the face of the planet.

“What the public need […] is something spectacular that grabs people in the gut”
James Balog

James’s desire was to capture what is perhaps the most visually compelling effect of climate change. Retreating glaciers are a clear indication of the effects of rising global temperatures and one (despite the attempts by some to highlight the minority which are advancing) which is hard to ignore. Of course the glaciers highlighted in the film are only a small proportion of global land ice (which has the power to raise sea level) but can be seen as an important “canary in the coal mine” demonstrating the processes which are happening in the really large ice sheets too. Over the last twenty years, mass loss of ice sheets on Greenland and Antarctica are estimated to have contributed 0.59 ±0.20 mm yr -1 to global sea level rise (Shepard et al., 2012). While that may seem like a small number, the effects over the next century could be dramatic, especially as, if last year’s unprecedented Greenland melt are anything to go by (
Tedesco et al., 2012), this rate could be accelerating.

“If you had an abscess in your tooth, would you go to dentist after dentist until one told you not to pull it out?”
James Balog

Before the screening there was an introduction to the film by Chris Shearlock, Sustainable Development Manager at The Co-operative Group who explained the Co-op’s involvement in the film, and their outlook on sustainable and ethical investment. The Co-op has invested £1billion in renewable energy, and he estimated that they have refused £300 million of investment opportunities in hydrocarbon extraction, and so when following the film, the questioning turned to exploitation of the soon-to-be summer sea ice free arctic the voice of the Co-operative was clear – that they will not be investing in hydrocarbon extraction. That question was dealt with very differently by Chris Barton, Head of International & Domestic Energy Security at the DECC who put forward the UK government’s current position that whilst we should reduce demand, in order to maintain cheap oil and gas for UK consumers “sensible” and regulated extraction in the arctic should be a priority for UK plc. What to do with the resulting CO2 emissions in order to hit the < 2 °C target? Well in Chris Barton’s mind carbon capture and storage will come to the rescue.

The debate moved to whether, as we are not an Arctic state, we can do anything about the regulation of commercial activity in a basin which is a combination of the territorial water of eight nation states, and open ocean controlled under the international law of the sea. The DECC view seemed to be that it is largely none of our business and out of our control, but interestingly Jane Rumble, Head of Polar Regions Unit at the FCO, had a different perspective. She suggested that we should be (and can be) working constructively through the Arctic Council, towards a similar regulatory framework to that which controls the other end of the Earth via the Antarctic Treaty, and by influencing Canada (one of the eight bordering nation states) through the commonwealth. Colin Manson, Director of Manson Oceanographic Consultancy and member of the IMO Polar Code working group spoke of the frustration of many in the shipping industry that talks on the Polar Code had stalled and encouraged UK intervention as a broker. He also pointed that one little talked about impacts of the opening up of the Northern Passage would be dramatic reductions in the time and fuel needed for bulk cargo shipping from the far east to Europe. With the representative routing of Shanghai – Rotterdam dropping to 5 weeks, vs the current 8 week route via the Indian Ocean. Colin, along I think with many in the audience, hoped thoughtful regulation and consideration of the impacts of this increased shipping through the arctic would come before it was too late.

Julia Slingo OBE, Chief Scientist at the Met Office closed proceedings with an impassioned plea to take care with the interpretation of our current generation of climate models following questions from the audience, and highlighted the importance of sustained development of what are our best hopes for accurate and precise predictions of future climate change.

All in all it was a fascinating day, and I was grateful to be exposed to a beautiful film, as well as an insight into the minds of those at the policy end of climate change science.

“We think we need new oil and gas production whether people like it or not”
Chris Barton, Head of International & Domestic Energy Security, DECC

This blog is by Dr Marcus Badger (Chemistry) at the University of Bristol
. He writes about the APPCCG meeting held on 5 March 2013.
Marcus Badger