There have been heatwaves in Slovenia and Australia, snow in Vietnam and the return of the polar vortex to North America. Britain has had its wettest winter in 250 years but temperatures in parts of Russia and the Arctic have been 10C above normal. Meanwhile, the southern hemisphere has had the warmest start to a year ever recorded, with millions of people sweltering in Brazilian and southern African cities.
According to the UN's World Meteorological Organisation (WMO), which monitors global weather, the first six weeks of 2014 have seen an unusual number of extremes of heat, cold and rain – not just in a few regions as might be expected in any winter, but right the way around the world at the same time, with costly disruptions to transport, power systems and food production.
Some climate scientists argue that there is nothing unusual in winter global temperature extremes but Omar Baddour, chief of the WMO data division, says the recent phenomena are almost certainly interlinked, with new computer models suggesting increased evidence of climate change.
"We are also seeing some unusual phenomenon, such as the polar vortex in North America, that is bringing unusually cold weather, which would not be automatically be considered to be due to climate change. However, there is some evidence that such unexpected surprises are also due to global warming."
But some scientists are cautious about linking extremes to climate change. "Looking for a signal of climate change in short-term weather does not make much scientific sense … There is however evidence for increasing heatwaves and in some measures, increasing precipitation," said Roger Pielke Jr, professor of environmental studies of the Centre for Science and Technology Policy Research at the University of Colorado.
"Human-caused climate change is real, poses risks and we should take action in terms of both mitigation and adaptation. [But] extreme events are a bad place to look for climate signals."
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