The Nasa climate scientists who claimed 2014 set a new record for global warmth last night admitted they were only 38 per cent sure this was true.
In a press release on Friday, Nasa’s Goddard Institute for Space Studies (GISS) claimed its analysis of world temperatures showed ‘2014 was the warmest year on record’.
The claim made headlines around the world, but yesterday it emerged that GISS’s analysis – based on readings from more than 3,000 measuring stations worldwide – is subject to a margin of error. Nasa admits this means it is far from certain that 2014 set a record at all.
Yet the Nasa press release failed to mention this, as well as the fact that the alleged ‘record’ amounted to an increase over 2010, the previous ‘warmest year’, of just two-hundredths of a degree – or 0.02C. The margin of error is said by scientists to be approximately 0.1C – several times as much.
As a result, GISS’s director Gavin Schmidt has now admitted Nasa thinks the likelihood that 2014 was the warmest year since 1880 is just 38 per cent. However, when asked by this newspaper whether he regretted that the news release did not mention this, he did not respond. Another analysis, from the Berkeley Earth Surface Temperature (BEST) project, drawn from ten times as many measuring stations as GISS, concluded that if 2014 was a record year, it was by an even tinier amount.
Its report said: ‘Numerically, our best estimate for the global temperature of 2014 puts it slightly above (by 0.01C) that of the next warmest year (2010) but by much less than the margin of uncertainty.
‘Therefore it is impossible to conclude from our analysis which of 2014, 2010, or 2005 was actually the warmest year… the Earth’s average temperature for the past decade has changed very little.’
Scientists disagree over its significance, but there is little doubt that the rapid warming of the 1980s and early 1990s has slowed – although greenhouse gas emissions have surged.
Bob Ward, of the Grantham Institute on Climate Change, said the new figures showed the notion that global warming had ‘stopped’ was a ‘myth’, although it had ‘temporarily slowed’. Since 1951, he added, the long-term trend was for warming of 0.12C per decade, and in his view, it would ‘pick up again unabated’ if emissions continued to rise.
However, if the long-term rate is 0.12C per decade, this would mean the world would be 1C or so warmer by the end of the century, not 4C-5C as some have claimed.
Climate sceptics insisted that the new figures showed the warming ‘pause’ had continued. Dr David Whitehouse, of the Global Warming Policy Forum, said ‘there has been no statistically significant warming trend since 1997’ – because the entire increase over this period was smaller than the error margin.
Dr Ed Hawkins, associate professor of climate science at the University of Reading, said the past 15 years had seen a slightly slower rate of warming.
But he added: ‘You have to take a longer view, because 15 years is too short a period. We expect natural fluctuations, volcanic eruptions and changes in solar output to sometimes slow and sometimes increase warming rates.’