This year’s global average surface temperature is likely to be the warmest on record according to data from the Met Office, and is expected to continue the trend showing 15 of the top 16 warmest years have happened since 2001.
These findings concur with the World Meteorological Organisation (WMO) findings also announced today.
2015 a more ‘clear-cut’ record
Provisional figures up to the end of October show this year’s near-surface global temperature as estimated from the HadCRUT dataset has been around 0.71 ±0.1 °C above the 1961-1990 average of 14.0 °C.
This is in-line with the Met Office’s forecast, issued in December 2014, which predicted 2015 global temperatures would be between 0.52 °C and 0.76 °C* above the 1961-1990 average, with a central estimate of 0.64 °C.
In HadCRUT, this year is clearly warmer than 2014, the previous nominal warmest year in the record, which was 0.57 ±0.1 °C above the 1961-1990 average.
Colin Morice, a climate monitoring scientist at the Met Office, said: “Last year was nominally the warmest year in our records but wasn’t much higher than the other top warmest years. This year the temperature is markedly warmer than anything we’ve previously seen in the 166-year record, meaning its position at the top of the rankings looks set to be much more clear cut.”
The HadCRUT dataset, jointly compiled by the Met Office and Climatic Research Unit at the University of East Anglia, uses data from more than 6, 000 observation sites around the world and observations from ships and buoys at sea. It is recognised as one of the world’s leading indices of global temperature.
Temperatures 1 °C above ‘pre-industrial’ for first time
2015 is set to mark the first time in the record that annual global temperatures reach 1 °C above ‘pre-industrial’ temperatures (taken here as an average of the 1850-1900 period*).
This is important because governments around the world have agreed the aim of trying to limit warming to 2 °C or less above pre-industrial to try to avoid the most dangerous impacts of climate change.
Leading independently-run datasets agree
Findings from HadCRUT are very similar to independently-run global temperature datasets compiled by the US National Oceanic and Atmospheric Administration and NASA Goddard Institute of Space Studies.
Information from all three datasets is included in an announcement from the World Meteorological Organization (WMO) on global temperature, which also concludes this year is likely to be the warmest on record.
Where did 2015’s warmth come from?
This year has seen a strong El Niño develop, with unusually warm sea surface temperatures across the Tropical Pacific, releasing heat into the atmosphere and pushing up global temperatures.
While this has contributed to 2015’s warmth, this is likely to be comparatively small compared to the long-term influence of warming caused by human greenhouse gas emissions.
This is backed up by research from the Met Office last year which showed global temperatures seen in recent years would be highly unlikely in a world without human influence on the climate.
What’s in store for the year ahead?
Last year saw record or near record warmth globally, this year is warmer still and the current expectation is that next year will also be warm.
This is due to two factors: firstly, the ongoing warming due to human influence, and secondly although the current El Niño is expected to peak around the end of this year, its main warming influence is usually felt in the months afterwards. For example, a strong El Niño peaked at the end of 1997 – but it was 1998 which went on to become a record (at the time) by some margin.
There are other natural factors – such as changes in longer term ocean cycles or volcanic eruptions – which could act to reduce global temperatures next year, so there will always be some uncertainty.
The Met Office will give more detail in the expected global temperature for 2016 when it publishes its forecast in the latter part of December.
* While late 19th century temperatures are commonly taken to be indicative of pre-industrial, there is no fixed period that is used as standard and a variety of other periods have been used for observational and palaeo datasets. There are limitations in available data in the early instrumental record, making the average temperature in the reference period less certain. There is not a reliable indicator of global temperatures back to 1750, which is the era widely assumed to represent pre-industrial conditions. Therefore 1850-1900 is chosen here as the most reliable reference period, which also corresponds to the period chosen by IPCC to represent a suitable earlier reference period.