David Concar

Blog Action Day: The physical impacts of climate change

One of the many challenges of being a diplomat specialising in climate change is keeping up with the latest science.

New evidence on the present and likely future impacts of global warming is being published all the time. But formal assessments by the UN’s Intergovernmental Panel on Climate Change appear only once every six years or so. The last one was in 2007 and only covered science published in peer review journals up to May 2006.

A lot has happened since then, both to the planet’s climate systems and the evidence base. Where to go for an informed view of the latest science?

I can recommend a “synthesis” report based on a conference held earlier this year in Copenhagen by the International Alliance of Research Universities. The report was published in English in June  but is now available in other languages too, including Chinese . Some of the world’s best climate experts were involved in writing it. Its stated goal is to reflect “solidly and accurately” the research produced since the last IPCC report. Importantly, it was subject to an extensive review process.

The report describes how the physical impacts of climate change are kicking in faster than previously thought. Ocean warming is now 50% greater than reported in the 2007 IPCC report. Estimates of future global sea level rise are double the IPCC projections. Ice caps and ice sheets are losing mass faster, and shrinking more in the summer. There is now more – and better – evidence on the threat posed by climate change to natural processes that enable land and oceans to act as crucial “sinks” for carbon.

The report analyses what all this means for the defining of  “dangerous” in the context of climate change. Many governments (including the UK’s) have a settled view that we need an international climate agreement strong enough to limit global warming to no more than 2 degrees above pre-industrial levels. Anything less we argue would be too risky.

But not all governments are explicitly supporting the 2-degree target or yet pledging actions in line with achieving it. So what does the latest evidence say about the risks of 2 versus, say, 3 or 4 degrees of warming?

In 2001 the IPCC assessed five categories of concern linked to climate change (eg the risk of extreme weather events or the risk of abrupt changes in large natural systems). Back then, the science indicated that limiting warming to no more than 2 degrees would be enough to avoid serious risks across all five categories. Sadly that is no longer the case. An updated version of the analysis in the new “synthesis” report assigns significantly higher levels of risk to 2 degrees of warming. For example, the risk of abrupt and irreversible changes in large natural systems increases from “very low” in the old assessment of 2 degrees to “moderate” in the new one. In other words, 2 degrees worth of risk in the new analysis resembles at least 3 degrees worth of risk in the old one.

The report concludes: “Although a 2 degree rise in temperature above pre-industrial remains the most commonly quoted guardrail for avoiding dangerous climate change, it nevertheless carries significant risks of deleterious impacts for society and the environment”.  

The issue of where we should agree to draw the line on climate change is of course fundamental to the international negotiations that will come to a head in Copenhagen in December. Some policy makers and governments will no doubt continue to suggest that aiming for 2 degrees is too ambitious and not justified by the science. The message I take from the latest research is just the opposite. Aiming for 2 degrees may not be ambitious enough. 

Posted at 13:45 15 October 2009 by David Concar  |  Comments[2]