Where are we on climate change?

Professor Sir Brian Hoskins, Director of the Grantham Institute for Climate Change and advisor to the UK government through the Committee on Climate Change, recently gave a talk at Imperial College London on the latest research and actions around climate change.

Global CO₂ levels are currently at 397ppm (parts per million), a level not seen for 4.5 million years. We have increased CO₂ levels in the atmosphere by 40% since the Industrial Revolution. While there has been a clear and significant increase in global temperatures since 1850, we have seen a hiatus on temperature rises in the last decade. While sceptics may use this as evidence to support their claims, a decade of cooler temperatures is not outside the range of predictions from climate models.

Global sea levels are rising 3mm per year. While the melting of the Western Antarctic and Greenland ice sheets is contributing around 1mm of this increase, it is unknown how likely this is to accelerate if we reach a threshold point of destabilisation. In the Arctic, recent pictures of the ice cap in mid-September (when it is at its minimum size) show it is half the average size it was in the last century. By 2050-2060 we would expect the arctic ice cap to have vanished come September.

We have seen some significant heat extremes in the past decade: the 2003 European heatwave, 2010 Russian heatwave and more recently the 2012 US drought. Work by NASA scientists Dr James Hansen and colleagues indicates a shift to more frequent and severe bouts of high temperatures. But it is not just heat extremes, as the climate changes we are also seeing cold extremes in certain locations despite remarkable warmth elsewhere. This indicates our ability to predict regional trends is much more limited than our ability to predict global averages and while we may, in the past have viewed climate change as a warming of the planet, now we are trying to understand it as a disruption of our climate systems, one that will have severe and varied results.

Extreme Weather Events on the Rise

Can scientists now say with a fair amount of confidence that extreme weather events such as the Texas heat wave last year, the Russian heat wave of 2010 and the European heat wave of 2003 are directly linked to global warming caused by humans?

In a new paper entitled ‘Perception of Climate Change’ NASA scientist James Hansen and two colleagues describe how climate change has increased the occurrence of unusually warm weather events in the past 30 years. There is only a small chance that the shift towards both higher temperatures and increased weather extremes would have happened in the absence of climate change.  Periods of extreme summertime temperatures have increased in geographic scope from less than 1% of the land’s surface in the base period of 1951 to 1980 to covering 13% in recent years.