There are many climatologists on our planet, some of them are truly standing out. Jean-Pascal van Ypersele, professor at UCL in Belgium, and Vice-chair of the IPCC, definitely belongs to those few. This is because he combines scientific authority and rationalism with a human heart of compassion and understanding for our world. I asked Prof. Ypersele about his opinion on the recent G8 decision to adopt 2ºC as the maximum for average global warming.

Prof. van Ypersele, you  have witnessed the climate change debate since a long time. Now, finally, the G8 officially announced that they accept 2ºC as a target for maximal global warming. Many people are breathing a big sigh of relief, and believe that we finally are on the right track. Are we?

Well, it is interesting to see the G8 recognizes that the target set by the European Union 13 years ago (Council of European Ministers, June 1996) has wide support. It is an important step in the right direction, even if science (and climate) has significantly evolved since 1996. The last IPCC assessment report (2007) has shown that the risks to a number of natural and human systems were assessed to be significantly higher for a 2°C global warming than they were assessed in the previous IPCC assessment (2001). If the same European ministers who decided to consider a warming above 2°C as dangerous were to revisit their decision today using the same criteria,  they would very likely have to conclude, on the basis of the latest IPCC report, that the threshold would have to be lower than 2°C by about half a degree. So, we are on a better track than previously, but there is still a long way to go. (more…)

Arctic sea-ice minimum 2007

Everybody knows that the sea-ice in the Arctic is melting. Now a new study shows just how severly this melting is proceeding.

2007 was the year where Arctic sea-ice gave us a scary example for what we have found true since then: that the IPCC report was not just describing true changes in our climatic system, but that these changes are often faster than some of the worst case scenarios of the climate models. The extent of the Arctic sea-ice had shrunk so much, that for the first time in human memory the Northwest passage was navigable (see Fig. 1).

If melting continues like that, then - so scientists fear - the summer Arctic sea-ice could be completely gone within 20 to 30 years; the tipping point for a complete melting of Arctic sea-ice in the summer even might have been crossed already (Lenton 2009). (more…)

Finally, the G8 has come to its senses in terms of climate change action. Now we need to make sure they know what needs to be done.

Often our work on climate change seemed like the attempt of a mom trying to explain to her child that it must not use her fingers to eat spaghetti -being heard but definitely not being taken seriously. Kids often only listen when they are afraid to lose their desert. Or they finally listen after strenuous years of nagging. At the latest at their graduation party. Now that’s a relief.

It seems quite the same with politicians; except that they sometimes never graduate. For how long have politicians been warned that inaction will lead to a catastrophe of a global scale with unimaginable consequences? We’ve nagged and pleaded, with mostly relatively little effect.

Now, finally, the G8 will adopt the 2°C limit of global warming - accepting the science that tells us that a warming by more than by 2°C from pre-industrial times will likely cause a passing of tipping points. (more…)

Fig. 1. Thawing permafrost. Image credit – Edward A.G.Schuur, University of Florida

Permafrost is the a subject in the climate change debate I have tried to not think about too much. It is just too scary to think about the vast amounts of carbon stored in frozen soils, ready to be released if global temperatures keep rising. But it seems to be time to finally take a closer look at what is happening in the most northern areas of our planet.

Areas like the northern parts of Siberia, Alaska, or Canada are cold enough that most parts of the ground are frozen - that is why it is called “permafrost” (Fig. 1). Only the uppermost layer is thawing in the summer, and gives room for plants to grow. This active layer can be 0.6 to 4 m thick. Even though some of the plant material decomposes, quite a bit of it does not. This is because the active layer is frozen during large parts of the year; and microbial processes that decompose organic material are significantly slowed down at low temperatures - the soil acts like a freezer for organic material.

When air temperature increases, then of course the soil warms as well: the active layer will stay unfrozen for a longer period of time during the year, and the deeper, permanently frozen area will start to thaw. At the same time, warmer temperatures increase microbial activity. Microbial activity, in turn, produces its own heat. With that, the decomposition of organic materials in the soil will proceed not only over a larger time span and over a larger area, but also at an accelerated rate. This positive feedback loop will accelerate with further warming, and could ultimately trigger an “irreversible process of thawing.” (more…)