2015 is the hottest year on record by a massive 0.13°C

Dr Gavin Schmidt, Director of the Goddard Institute of Space Studies (GISS), NASA and Dr Thomas Karl, Director of the National Centers for Environmental Information (NCEI), NOAA have just given a press conference to to announce the annual average global temperature results and discuss the most important weather and climate events of the year.

You will not be surprised to know that 2015 was yet another hottest year ever recorded in the instrumental record, beating 2014 by a huge 0.13 °C. It was 1.25 °C hotter than pre-industrial. It is now 106 years since there was a "coldest year on record". (Gavin Schmidt said that 2015 would have broken the record even without the El Niño, though presumably by not as much.)

Anyone who tries to tell you it hasn't warmed since 1996, or 1997, or 1998, is dead wrong. See for yourself:

Figure 1 | Annual global mean surface temperature. Anomaly from the 1881-1910 mean. Data source: GISS NASA.

The average global temperature in 2015 was:

• 0.13 °C hotter than in 2014
• 1.33 °C hotter than the coldest year in the record (1909)
• 0,24 °C hotter than the average for 1998
• 1.25 °C hotter than pre-industrial (ballpark)

Note about the ballpark: I took the pre-industrial benchmark to be 0.3 °C cooler than 1900, from this recent article by Professor Michael Mann in Huffington Post.

Decadal changes

On a decadal time scale, last year is hauling the chart upwards, being way above the latest decadal average. Below is a chart showing decadal changes, starting from the sixth year in each decade to show the full decade up to December 2015.

Figure 2 | Decadal global mean surface temperature. Anomaly from the 1881-1910 mean, from 1886-1895 to 2006-2015. Data source: GISS NASA

Here is another decadal chart, starting from the first year in each decade. In this case the most recent decade has six years of data so far, from 2011 to 2015 inclusive.

Figure 3 | Decadal global mean surface temperature. Anomaly from the 1881-1910 mean, from 1881-1890 to 2011-2015.. Data source: GISS NASA

Where did it get hot and where was it colder?

To see where it's been extra warm this past 12 months, here is the map from NOAA showing the land and ocean temperature percentiles, with the record warmest and record coldest. I've added some arrows.

Figure 4 | January–December 2014 Blended Land and Sea Surface Temperature Percentiles Source: NOAA

Hottest years in order

Below is a chart showing the hottest years, starting with 2015 on the left. As the chart and the table underneath show, fifteen of the sixteen hottest years were this century. 2015 broke the mould by being a huge 0.13 °C hotter than the previous hottest year. The previous biggest jump (just in the top 20) was less than half that, at 0.06 °C. I checked again. There have been two occasions when there were bigger hikes from one year to the next in the past twenty years: 1997 to 1998 and 2004 to 2005. It has happened on average about one in ten years since 1880.

Figure 4 | Twenty hottest years on record. Anomaly from the 1881-1910. Data source: GISS NASA

Data source: GISS NASA

	Year	Anomaly from 1881-1910 mean (°C)
1	2015	1.12
2	2014	0.99
3	2010	0.97
4	2005	0.94
5	2007	0.91
6	2013	0.90
7	2009	0.89
8	1998	0.88
9	2002	0.89
10	2006	0.88
11	2012	0.88
12	2003	0.87
13	2011	0.85
14	2001	0.79
15	2004	0.79
16	2008	0.78

Watch the world warming

A video from NASA, showing the warming from 1880 to 2015:

Update: Gavin Schmidt updated this chart he provided last year, on Twitter and at realclimate.org.

Stay safe

As if to emphasise the fact that climate change brings extreme weather, I see that the east coast of the USA is bracing for the possibility of a "blockbuster" storm event, an "epic blizzard" which could bring:

• Record snowfalls, particularly to Washington DC (big snows elsewhere but unlikely to be a record)
• Fierce winds
• Storm surges, and twenty foot waves along the mid-Atlantic coast (especially from New Jersey to the Delmarva Peninsula)
• blackouts for lots and lots of people
• A raucous din from science deniers saying "see, it's record snow. Global warming is a hoax".

Or it might not. It's still too soon to say, although Bob Henson wrote: "computer models were in remarkable agreement late Tuesday" - then again - models, huh!

Protests from deniers at WUWT

WUWT are already protesting the hot planet. Bob Tisdale has posted two protest articles in quick succession (archived here and here). He put "record high" in quotation marks presumably to show that he doesn't believe the data. He makes a habit of accusing scientists of fraud and fakery. He's not a man of good character. A sleaze as well as a science denier. Bob wrote:

I suspect Tom Karl and Gavin Schmidt won’t bother to tell the public that lower troposphere temperature data were far from record highs in 2015.

He was wrong. They did "tell the public" about the lower troposphere temperatures in their main presentation - and said the annual temperature wasn't a record (without prompting by anyone).

Bob's also wrong about the upper air temperatures being far from record highs. On an annual basis the lower troposphere temperature record makes 2015 the third hottest year on record, which is not far at all. As well as that, the last three months of the record each broke the record for that month. That is, there was a record hot October, a record hot November and a record hot December.

Bob Tisdale didn't bother to tell the WUWT public about the Berkeley Earth record

What Bob Tisdale didn't tell his readers was that as far as the surface temperatures go (which is where we live, after all), there is another independent data set that also posted a record hot year. Elizabeth Muller of Berkeley Earth wrote:

According to new Berkeley Earth analysis, 2015 was unambiguously the hottest year on record. For the first time in recorded history, the Earth’s temperature is clearly more than 1.0 C (1.8 F) above the 1850-1900 average. 2015 was approximately 0.1 degree C (about 0.2 degrees F) hotter than 2014, which had tied with 2005 and 2010 as the previous hottest years. 2015 set the record with 99.996% confidence. The analysis covered the entire surface of the Earth, including temperatures from both land and oceans. 

She also said:

The most important things we can do to mitigate global warming include energy efficiency and the increased use of renewables, natural gas, and nuclear power. It is time for us to stop being picky about which is the very best solution to global warming – we need all solutions that are available to us today 

References and further reading

• NASA, NOAA Analyses Reveal Record-Shattering Global Warm Temperatures in 2015 - Press release from NASA
• 2015 is Earth's warmest year by widest margin on record; December 2015 temperature record warm - December global report from NOAA
• Global Analysis - Annual 2015 - NOAA
• Global Analysis - Annual 2015 - report from NOAA, January 2016
• GISS Surface Temperature Analysis (GISTEMP) - NASA, with links to data
• How Close Are We to 'Dangerous' Planetary Warming? - article by climate scientist Michael Mann at Huffington Post - December 2015
• Mid-Atlantic Braces for Potentially Epic Blizzard - article by Bob Henson on Weather Underground, January 2016
• 2015 Unambiguously the Hottest Year on Record - press release from Berkeley Earth, January 2016

From the HotWhopper archives

• Three hottest evers in succession for lower troposphere - January 2016
• Confirmed - 2014 was the hottest year on record - January 2015
• Let's just clear this up once and for all. Last year was HOT! - January 2015