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Why has the year 2014 been so hot? Why has the year 2014 been so hot?
(4 months later)
This year seems to be on track to be the hottest globally and in the UK. But what does this mean and what are the wider implications?This year seems to be on track to be the hottest globally and in the UK. But what does this mean and what are the wider implications?
Where do the figures come from?
For the UK, the Met Office operates weather stations around the country and collects time-series data that show variations in the temperature over months, seasons and years.For the UK, the Met Office operates weather stations around the country and collects time-series data that show variations in the temperature over months, seasons and years.
For the UK, the mean temperature from 1 January to 25 November is 1.6°C above the long-term average.For the UK, the mean temperature from 1 January to 25 November is 1.6°C above the long-term average.
That means 2014 is currently the warmest in the Met Office UK series dating back to 1910.That means 2014 is currently the warmest in the Met Office UK series dating back to 1910.
This year is also set to be one of the warmest on record in the Central England Temperature (CET) series, which goes back to 1659 and is the longest instrumental temperature series in the world.This year is also set to be one of the warmest on record in the Central England Temperature (CET) series, which goes back to 1659 and is the longest instrumental temperature series in the world.
The World Meteorological Organization (WMO) also says 2014 is on track to be the warmest globally.The World Meteorological Organization (WMO) also says 2014 is on track to be the warmest globally.
According to the body, this is largely due to record high global sea surface temperatures.According to the body, this is largely due to record high global sea surface temperatures.
The WMO is the UN's authoritative voice on global weather and climate.The WMO is the UN's authoritative voice on global weather and climate.
Both the Met Office and the UN organisation say that the observed temperatures are consistent with what would be expected from human-induced climate change.Both the Met Office and the UN organisation say that the observed temperatures are consistent with what would be expected from human-induced climate change.
What data is used to analyse global temperatures?
The WMO's analysis is based on three complementary datasets. One is maintained by the UK Met Office's Hadley Centre and the University of East Anglia (UEA) which is known as HadCrut4.The WMO's analysis is based on three complementary datasets. One is maintained by the UK Met Office's Hadley Centre and the University of East Anglia (UEA) which is known as HadCrut4.
The second is overseen by the US space agency Nasa and is known as the Nasa GISS dataset.The second is overseen by the US space agency Nasa and is known as the Nasa GISS dataset.
The third is maintained by the US National Oceanic and Atmospheric Administration (Noaa).The third is maintained by the US National Oceanic and Atmospheric Administration (Noaa).
Overall, they show a very similar story, but there are differences between them - mainly to do with the way that each group treats gaps in the data.Overall, they show a very similar story, but there are differences between them - mainly to do with the way that each group treats gaps in the data.
What else can affect variation in global temperatures?
Record warm years in the global temperature record are frequently associated with the temporary warming influence of the climate system known as El Nino.Record warm years in the global temperature record are frequently associated with the temporary warming influence of the climate system known as El Nino.
El Nino occurs when warmer than average sea surface temperatures in the eastern tropical Pacific combine, in a self-reinforcing loop, with atmospheric pressure systems. This can affect global weather patterns.El Nino occurs when warmer than average sea surface temperatures in the eastern tropical Pacific combine, in a self-reinforcing loop, with atmospheric pressure systems. This can affect global weather patterns.
But the high global temperatures in 2014 occurred in the absence of a full El Nino. During the year, sea surface temperatures rose nearly to El Nino thresholds but this wasn't accompanied by an atmospheric response.But the high global temperatures in 2014 occurred in the absence of a full El Nino. During the year, sea surface temperatures rose nearly to El Nino thresholds but this wasn't accompanied by an atmospheric response.
Scientists think the persistence of above average temperatures in the tropical west Pacific Ocean stifled the atmospheric response that is necessary for an El Nino to mature.Scientists think the persistence of above average temperatures in the tropical west Pacific Ocean stifled the atmospheric response that is necessary for an El Nino to mature.
I thought there was a pause in global warming?
Global mean surface temperatures rose rapidly from the 1970s, but were relatively flat over the 15 years prior to 2013.Global mean surface temperatures rose rapidly from the 1970s, but were relatively flat over the 15 years prior to 2013.
Many studies have reinforced a link between uptake of heat by the oceans and the "pause".Many studies have reinforced a link between uptake of heat by the oceans and the "pause".
The high surface temperatures of the Pacific and other parts of the world's oceans might suggest that the pause is coming to an end, but there is no evidence yet to support this.The high surface temperatures of the Pacific and other parts of the world's oceans might suggest that the pause is coming to an end, but there is no evidence yet to support this.
Climate scientists need more than one warm year to discern underlying trends.Climate scientists need more than one warm year to discern underlying trends.
A year of extremes
The WMO report highlights a number of record-breaking weather events around the world:The WMO report highlights a number of record-breaking weather events around the world: