May 27, 2021

expert reaction to the Global Annual to Decadal Climate Update

The Global Annual to Decadal Climate Update has been published today, led by the UK Met Office and issued by the World Meteorological Organization (WMO).

Prof Rowan Sutton, Director of Climate Research at the National Centre for Atmospheric Science (NCAS), University of Reading, said:

“A single year in which global temperatures exceed 1.5C above pre-industrial levels is quite different to temperatures staying above this level permanently, but it would be entirely appropriate to treat it as a warning of events to come.  It would give us new insights into the warmer worlds we are heading toward, for example illustrating diverse impacts on people and natural systems in many different parts of the world.”

Dr Joeri Rogelj, Director of Research at the Grantham Institute, Imperial College London, said:

“The 1.5°C in the Met Office announcement should not be confused with the 1.5°C limit in the Paris Agreement. The Paris targets refer to global warming – that is, the temperature increase of our planet once we smooth out year-to-year variations. Even in a stable climate, global temperatures differ from year to year because of noise in the climate system. For example, a year with a climate phenomenon known as El Niño will be slightly warmer than other years and therefore doesn’t represent the long-term warming. 

“In a world that has warmed by 1.5°C we expect half of the years to be warmer than 1.5°C, and the other half cooler. A single year hitting 1.5°C therefore doesn’t mean the Paris limits are breached, but is nevertheless very bad news. It tells us once again that climate action to date is wholly insufficient and emissions need to be reduced urgently to zero to halt global warming.”

Prof Richard Allan, Professor of Climate Science, University of Reading, said:

“Crossing the threshold of 1.5 degrees Celsius above pre-industrial global surface temperature in any single year is not in itself significant. Imperfect observations and fluctuating weather patterns can add or subtract a few tenths of a degree causing this threshold to be temporarily crossed in one year. However, considered as part of a long term warming trend and consulting the wealth of scientific evidence confirms that we are on trajectory for whole decades, such as the 2030s or 2040s, to be 1.5 degrees or even 2 degrees warmer on average globally than before industrialisation. This warming path will lead to increasingly dangerous worldwide impacts of climate change unless our greenhouse gas emissions are rapidly and drastically cut.”

Prof Myles Allen, Professor of Geosystem Science, University of Oxford, said:

“To limit global warming to 1.5C – or what the parties to the Paris Agreement thought 1.5C meant when they signed it – we need to hit the brakes on emissions now and stop global warming in the next 30 years or so. That hasn’t changed, apart from the fact that 5 years have passed since Paris and we are still only talking about hitting the brakes.

“Most of this latest ‘increased risk’ of temperatures wobbling over 1.5C (which is not the same as warming reaching 1.5C – we probably hit 1.5C in April 2016, just for a month or so) is due to a downward revision of late-19^th-century temperatures relative to today. Climate change hasn’t just got ‘worse than we thought’, unless people use this latest news as an excuse to give up.”

Prof Ed Hawkins, Climate research scientist, University of Reading, said:

“This new forecast suggests that there is a reasonable chance we will experience an annual average global temperature of more than 1.5C above pre-industrial levels in the next few years. This is an indication that we are fast approaching the temperature levels that the Paris Agreement aims to avoid. We have already experienced a couple of months in 2016 when the global temperature was more than 1.5C above pre-industrial levels and, as global temperatures continue to rise, it is inevitable that we will continue to temporarily cross 1.5C before we exceed it for more sustained periods. Global greenhouse gas emissions need to decline rapidly to net-zero to avoid crossing these limits permanently. However, none of the temperature limits set out in the Paris Agreement constitute a ‘safe’ level – we are already experiencing the consequences of climate change and these consequences will continue to become more severe if global temperatures rise further.”

The Global Annual to Decadal Climate Update was published at 1.01am on Thursday 27 May 2021.

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