Critics like to cite research showing the rise in the world’s average surface temperatures has slowed down since 1998. But is it true?
Q: What is the “pause” in global warming?
A: Surface temperatures around the world have not increased as fast over the past decade than in previous decades. This levelling off in global average temperatures has been interpreted as a pause or hiatus in global warming.
Q: Does this mean that global warming has stopped?
A: No. The UN’s Intergovernmental Panel on Climate Change, which is the combined expertise of thousands of climate scientists, says that each of the past three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. In the northern hemisphere, the period from 1983 to 2012 was likely to be the warmest 30-year period for the last 1,400 years.
Q: Can this pause be explained?
A: It is likely to be a combination of factors. Heat from the Earth’s surface has been transferred to the deep ocean, for instance. Recent research has shown that deeper layers of the Pacific Ocean in particular are warming 15 times faster than during other periods of global warming.
Q: What is the latest explanation for the pause?
A: Simply put: the pause does not really exist. When temperature readings for the Arctic – which do not exist for much of this remote region – are put into the calculations, global temperatures continue to rise as before. Scientists have had to assume that the Arctic is warming about as fast as everywhere else, which they knew to be an under-estimate. However, when Kevin Cowtan and Robert Way worked out a way of estimating Arctic surface temperatures more accurately, the global warming signal returned and the “pause” was effectively eliminated.
Q: So is the problem solved?
A: It’s a potential solution but it is likely to be one of several reasons why temperatures have stalled. Only longer-term monitoring will show whether it’s a temporary aberration.