The main difference between this report and the previous one from 2001 is that the IPCC now qualifies human activities as the ‘very likely’ (>90% chance) cause for the global warming. In 2001 the term ‘likely’ was used. Industrial activities and agriculture have pushed up the levels of greenhouse gases carbon dioxide, methane and nitrous oxide to levels unprecedented in geological history.

In fact, global warming has only just begun. Between 1990 and 2005 the average global temperature increased by 0.33 degrees Celsius. But the rate of increase is accelerating. For the next two decades the IPCC predicts a warming of 0.2 degrees Celsius per decade. More heat waves and floods are ‘very likely’. More intensive tropical storms on the scale of Katrina are considered ‘likely’. Because of the timescales associated with climate processes and feedbacks, anthropogenic warming and sea level rise will continue for centuries, even if greenhouse gas emissions were to be stabilised as of now.

Is this already alarming enough? Not yet, German climatologist Stefan Rahmstorf writes in a Science article that was published last week, “Previous projections, as summarised by the IPCC, have not exaggerated but may in some respects even have underestimated the change, in particular for sea level.” Rahmstorf and colleagues arrive at this conclusion after comparing the predicted sea level rises with the observed data from 1990 onwards. Satellite data show a rise of 3.3 millimetres per year, while the IPCC estimated 2 millimetres per year as most probable. Thermal expansion of the oceans and glacier melting were the main contributors. But increasing contributions are to be expected from Greenland and Antarctica.

“Clearly, the 20 percent CO2 reduction that the European Commission agreed upon last January is not enough,” according to Dorette Corbey, socialist member of the European Parliament. “The reduction should have been 30 percent in order to limit global warming to 2 degrees maximum,” Corbey says. She thinks Europe should take the political lead in cutting CO2 emissions. “Every week a new coal plant opens up in China. We should make sure they should be equipped to capture and store the greenhouse gases.”

After this ‘scientific basis’ report, IPCC will publish other scientific reports in April. These coming reports will cover how to adapt to climate change, and how to mitigate climate change with measures for greenhouse gas emission reduction.