Climate change is kicking in faster that expected, and the global threshold of 2^oC is now considered the line between dangerous and extremely dangerous climate change. What will it take to avoid this highway to hell?

WHO: Kevin Anderson, Tyndall Centre for Climate Change Research, School of Mechanical, Aerospace and Civil Engineering, University of Manchester, UK  and School of Environmental Sciences and School of Development, University of East Anglia, Norwich, UK
Alice Bows, Sustainable Consumption Institute, School of Earth, Atmospheric and Environmental Sciences, University of Manchester, UK

WHAT: Some carbon budgetary truths for the world – how much do we have left to burn and when do we have to stop it by?

WHEN: 13 January 2011

WHERE: Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences. Phil. Trans. R. Soc. A vol. 369, no. 1934

TITLE: Beyond ‘dangerous’ climate change: emission scenarios for a new world

Have you ever seen one of those reality TV shows where a person who is hopeless with money is given some budgeting ‘real talk’ and taught to live within their means? This paper is going to do that for your carbon budgets.

Humans love to procrastinate – we’re great at it. And despite all the new semester resolutions of keeping on top of the work this time, it inevitably leads to last minute late night exam cramming. However, it looks like climate change doesn’t have this problem. Currently, the arctic ‘death spiral’ is decades ahead of melting from climate change schedule, the Great Barrier Reef in Australia is already 50% bleached and dead and the drought predictions for the south west of the USA are also ahead of schedule.

This means that the globally declared point that we shall not pass for global warming of 2^oC has now been upgraded from the line between acceptable and dangerous climate change to the border between dangerous and extremely dangerous climate change. Congratulations on the promotion 2^oC?

So now that procrastinating past 2^oC is looking like a dangerous decision, what do we need to do about it?

These researchers looked at the Copenhagen Accord from the 2009 UNFCCC negotiations (remember the non-binding one?) and it states that we must act to prevent going above 2^oC of global warming on the basis of science and equity. Since it’s the cumulative emissions that are really going to bite us, the researchers decided to work from the end point of preventing 2^oC in different scenarios and then worked the carbon budgets backwards to see if we have a chance of meeting the 2^oC goal and how we could do it.

The UN separates the UNFCCC agreement into two groups: Annex 1 countries (which is the developed world) and non-Annex 1 countries (the developing world). Keeping with the ideal of equity, the scenarios in this paper allow for emissions to grow in the developing world longer than they can grow in the first world. However, the paper did point out that if developing nations grow into developed fossil fuel economies, their emissions will outstrip world emissions from the industrial revolution to the 1950s, so mitigation in the developing world is going to be increasingly important really fast.

The paper does three scenarios and then tweaks each one. The first scenario only counts CO₂ emissions which allows it to be more accurate, but doesn’t include other greenhouse gases. The second scenario includes all six main greenhouse gases which makes it less accurate (more variables) but also more realistic. The third scenario looks at what is currently considered ‘politically possible’ in terms of emissions reductions. It gets long, so I’ll provide a handy summary table too!

Interestingly, the Bill McKibben budget of 565 Gigatonnes (Gt) of carbon (2055 Gt of CO₂) from his Rolling Stone article is not considered here, because the chance of blowing past the 2^oC limit is too high.

Here’s how they worked out:

CO₂ only with a small budget
If we have a carbon budget of 1321 Gt CO₂ and emissions from the developing world grow at less than 3% per year until 2015, and reduces by 6% per year after 2020, and the first world reduces their emissions from now by 11% per year, we have a 36% of still causing extremely dangerous climate change.

If we do the above but the developing world’s emissions grow until 2025, they’ve spent the whole carbon budget at once and we blow past 2^oC. But if the developing world’s emissions grow at less than 1% until 2025 and they reduce their emissions by 7-8% per year while the first world reduces by 11% per year from now, then there’s a 37% chance of causing extremely dangerous climate change. The researchers described this one as ‘plausible but highly unlikely’.

CO₂ only with a bigger budget
So what happens if we’re a bit more realistic and increase the burnable budget a bit? If we have a carbon budget of 1578 Gt CO₂ and emissions from the developing world grow by 4% per year until 2015, first world emissions don’t grow and global emissions reduce by 5-6% per year from 2015, we have a 50% chance of causing extremely dangerous climate change.

If there is a 5 year delay and emissions in the developing world grow by 4% per year until 2020, and then reduce by 7-8% per year after that while the first world reduces by 7-8% per year from 2010 (yes, from two years ago), then the 5 year delay bumps us up to a 52% chance of causing extremely dangerous climate change, even with the faster reductions. Given we needed to start two years ago, that one’s out too.

If the developing world misses the 7-8% per year reduction targets above and only reduce emissions by 4-5% per year, they spend all the carbon budget and we either blow past 2^oC or first world emissions fall immediately to zero in 2015. Also not workable then.

Counting all the gases with a small budget
If we include all the other greenhouse gases like methane and nitrous oxide (which means we start talking CO₂ equivalent because otherwise it’s really unwieldy to count), we can also count emissions for food production for the 9 billion people we’re going to have on the planet by 2050, which will be around 6 Gt Co₂e per year (animals fart methane and crops need nitrogen among other things) and further reduces the carbon budget.

If the budget is 1376 Gt CO₂e and the developing world’s emissions grow at less than 3% per year until 2015, emissions in the first world need to drop to zero in 2015. So that budget is bust too.

Counting all the gases with a bigger budget
If the budget is 2202 Gt CO₂e and the developing world increases emissions by less than 3% per year until 2015 and then decreases by 6% per year and the first world reduces emissions by 3% per year until 2020 and then 6% per year after that, we have a 39% chance of causing extremely dangerous climate change.

If the developing world grows at 3% per year until 2020 and then reduces emissions by 6% per year, the first world needs to reduce emissions by 10% per year from 2010. So that budget is also bust.

If the developing world only grows at 1% per year until 2025 and reduces by 4-5% per year, the first world’s emissions need to be flat to 2014 and reduce by 6% per year after that. If we could do that we would have a 38% chance of causing extremely dangerous climate change.

But here’s the problem; currently what is considered politically and economically possible for reducing carbon emissions is reductions of 3% per year. Which blows all of these budgets.

If we only counted the CO₂,had a budget of 2741 GtCO₂ (which is higher than any of the budgets above) and reduced our emissions by 3% per year from 2015 in the first world and 2030 in the developing world, we have an 88% chance of causing extremely dangerous climate change.

If we counted all the gases and had a larger budget of 3662 Gt CO₂e with reductions of 3% per year as above, we get the same result. This means that business as usual is actually business on the way to 4^oC of global warming, which has been described by the one of the authors of this paper Kevin Anderson as

‘incompatible with organized global community, is likely to be beyond ‘adaptation’, is devastating to the majority of ecosystems & has a high probability of not being stable i.e.  4°C would be an interim temperature on the way to a much higher equilibrium level’

Basically, what we’re currently doing is going to fail spectacularly in the near future. And since physics doesn’t negotiate we can’t get an extension on this one. If we are to make any of the carbon budgets above, society needs to be reducing carbon emissions at a much higher rate than we currently are.

I’d like to finish with the conclusion from the paper, because I think their version of climate tough love is excellent:

This paper is not intended as a message of futility, but rather a bare and perhaps brutal assessment of where our ‘rose-tinted’ and well intentioned (though ultimately ineffective) approach to climate change has brought us. Real hope and opportunity, if it is to arise at all, will do so from a raw and dispassionate assessment of the scale of the challenge faced by the global community. This paper is intended as a small contribution to such a vision and future of hope.