July 2018 Global Temperature Update

July 2018 Global Temperature Update

image1.png

Heat waves seemed unusually widespread in July, as the media reported extreme heat in Europe, the Middle East, northern Africa, Japan and western United States.  Extreme heat contributed to extensive wildfires in the western United States, Greece and Sweden, with fire extending into the Arctic Circle.  

The left map is the global distribution of temperature anomalies with our usual 1200 km smoothing; the right map has 250 km smoothing and uses only meteorological stations (no sea surface temperatures).   Area-weighted warming over land (1.14°C) is 1.5 times larger than global warming (0.78°C), consistent with data for the past century (see graphs at http://www.columbia.edu/~mhs119/Temperature/T_moreFigs/).

Globally July 2018 was the third warmest July since reliable measurements began in 1880, 0.78°C warmer than the 1951-1980 mean.  The warmest Julys, in 2016 and 2017, were 0.82°C and 0.81°C, respectively.  July 2018 temperature was +1.06°C relative to the 1880-1920 base period, where the latter provides our best estimate of pre-industrial global temperature.

It is incorrect to describe the July 2018 climate conditions in the global hotspots as a “new normal” climate for those regions.  Hotspots move from one summer to another.  Sweden, for example, may have a much cooler summer next year.  However, the chance of having such extreme conditions is increasing dramatically.  Realistic description of the changing climate is perhaps shown best by our shifting “bell curves” for seasonal temperature anomalies (Regional Climate Change and National Responsibilities).

Figure 2, from our paper, shows that global warming has greatly increased the frequency or chance of an extreme hot summer, e.g., two standard deviations or more warmer than average 1951-1980 climate.  The bell curve is shifted by 1-1.5 standard deviations by 2005-2015 in the regions shown in Figure 2.

An important point is that the bell curves are continuing to shift, which is another reason not to suggest a fixed “new normal.”  How much has the bell curve continued to shift in just the past few years?

The 2015-2018 global temperature relative to 1951-1980 is +0.90, which compares with +0.66 for the period 2005-2015.  To a good approximation an increase of global warming from +0.66 to +0.90°C increases the rightward shift of the bell curve shown for 2005-2015 by the factor 0.90/0.66 ~ 1.36.

  Figure 2.  Bell curves that define the frequency of local temperature anomalies relative to 1951-1980 base period.  Numbers above maps are % of globe covered by the selected region.  ‘Shift’ and ‘width’ refer to 2005-2015 data.

Figure 2. Bell curves that define the frequency of local temperature anomalies relative to 1951-1980 base period.  Numbers above maps are % of globe covered by the selected region.  ‘Shift’ and ‘width’ refer to 2005-2015 data.

This large warming and movement of the bell curve, if it is representative of the coming decade, is an acceleration of the warming trend.  Of course, a strong El Nino (Figure 3) contributed to 2015-2018 warmth.  However, we will argue that the present 12-month running mean (Fig. 3) has already reached the inter-El Nino minimum global temperature, at a value that is above the trend line for the average.

If the latter assertion is correct, we may have entered a period of accelerated global warming.  Jeremy Grantham, in The Race of Our Lives Revisited, draws that conclusion from comparison of global temperatures at the peaks of the last two El Ninos.  An acceleration of warming is consistent with recent acceleration of climate forcings described in Young people's burden: requirement of negative CO2 emissions.  We will take a closer look at acceleration of global warming in our next Communication

  Figure 3.   Global surface temperature relative to 1880-1920 based on GISTEMP analysis (Hansen, J., Ruedy, R., Sato, M., and Lo, K.:   Global surface temperature change , Rev. Geophys., 48, RG4004, 2010.).

Figure 3.  Global surface temperature relative to 1880-1920 based on GISTEMP analysis (Hansen, J., Ruedy, R., Sato, M., and Lo, K.:  Global surface temperature change, Rev. Geophys., 48, RG4004, 2010.).

Climate shifts in the subtropics in the summer and in the tropics all year, as shown if Figure 4, are larger than at higher latitudes, with the unit of measurement being the standard deviation of local temperature.  Warming in these regions is particularly important, because the regions were already hot without added warming.  There is a danger that these regions will become less livable, increasing the pressures for migration, as discussed in Regional Climate Change and National Responsibilities.

  Figure 4.   Bell curves that define the frequency of local temperature anomalies relative to 1951-1980 base period.  Numbers above maps are % of globe covered by the selected region.  ‘Shift’ and ‘width’ refer to 2005-2015 data.

Figure 4.  Bell curves that define the frequency of local temperature anomalies relative to 1951-1980 base period.  Numbers above maps are % of globe covered by the selected region.  ‘Shift’ and ‘width’ refer to 2005-2015 data.


To receive our monthly Global Temperature Updates, please subscribe to this list:

http://eepurl.com/bnhnMT

To receive my online communications, please subscribe to my email list:

http://eepurl.com/lM2z

June 2018 Global Temperature Update

June 2018 Global Temperature Update

june temp fig1.png

Globally June 2018 was the third warmest June since reliable measurements began in 1880, 0.77°C warmer than the 1951-1980 mean. June 2018 temperature was +1.07°C relative to the 1880-1920 base period, which provides our best estimate of pre-industrial global temperature. 2015 and 2016 June anomalies were 0.80°C and 0.79°C, respectively, and 1998 tied with 2018 at 0.77°C.

The left side of the figure above shows the global distribution of June 2018 temperature, and the right side compares temperatures in the years 2015-2018 month by month. Note that temperature began rising in the latter part of 2015 as an El Nino was developing. That late 2015 warming led to record 2016 global heat. Some ocean models predict that an El Nino may develop later this year, in which case 2019 could be a very hot year. Historical precedence does not favor the occurrence of two strong El Ninos separated by only 3 years. On the other hand, the human hand may be altering history.

January-June this year was the 3rd warmest on record as shown below.

june temp fig2.png

To receive our monthly Global Temperature Updates, please subscribe to this list:

http://eepurl.com/bnhnMT

To receive my online communications, please subscribe to my email list:

http://eepurl.com/lM2z

May 2018 Global Temperature Update

may 2018 global temp fig1.png

May 2018 global temperature, at 0.82°C relative to the 1951-1980 base period, was the fourth warmest May since reliable measurements began in 1880.  The warmer Mays were in 2016 (+0.91°C), 2017 (+0.88°C) and 2014 (+0.85°C).  Northern Hemisphere spring (March-April-May) 2018 was the third warmest spring at 0.86°C (See the figure above), while the warmest were 2016 (1.10°C) and 2017 (0.97°C).  Note that the most of the U.S. was extremely cold in April and very warm in May.

Using the base period 1880-1920 which provides our best estimate of pre-industrial temperature, the May 2018 anomaly was 1.09°C.  Post-El Nino cooling has probably bottomed out, given that equatorial Pacific Ocean temperatures have begun to rise (See the left side of the figure below).  We conclude that global warming, with short-term variability excluded, has reached the level of at least +1.1°C relative to pre-industrial temperature.

may 2018 global temp fig2.png

To sign up for our monthly update of global temperature (Maps and Graphs), click here.
(http://columbia.us1.list-manage1.com/subscribe…)

Additional figures are on our global temperature web page.
(http://www.columbia.edu/~mhs119/Temperature/)

APRIL 2018 GLOBAL TEMPERATURE UPDATE

April 2018 Global Temp Update figure.png

Two-thirds of North America was very cold in April (left side of figure above), but globally April 2018, at 0.86°C relative to the 1951-1980 base period, was the third warmest April since reliable measurements began in 1880.  The warmest Aprils were in 2016 (+1.07) and 2017 (+0.92°C)!

The right side of the figure above compares monthly temperatures in the years 2015-2018. 

Post-El Nino cooling has probably bottomed out, given that equatorial Pacific Ocean temperatures have begun to rise.  We conclude that global warming, with short-term variability excluded, has reached the level +1.1°C relative to pre-industrial temperature, as shown in the figure below.

Note that base period 1880-1920, used for the figure below, provides our best estimate of pre-industrial temperature, as discussed in our Young People’s Burden paper (Earth System Dyn., 8, 1-40, 2017).

Also note that the reason we employ base period 1951-1980 in the figure above is the absence of earlier data for Antarctica, much of the Southern Ocean, and parts of Africa and South America.  There are enough data points to define a global mean temperature, but not to define a global map.

April 2018 Global Temp Update figure2.png

To sign up for our monthly update of global temperature (Maps and Graphs), click here.
(http://columbia.us1.list-manage1.com/subscribe…)

Additional figures are on our global temperature web page.
(http://www.columbia.edu/~mhs119/Temperature/)

March 2018 Global Temperature Update

pic1.png

Globally March 2018 was the sixth warmest March since reliable measurements began in 1880, 0.89°C warmer than the 1951-1980 mean.  March temperature was +1.16°C relative to the 1880-1920 base period that provides our best estimate of pre-industrial global temperature.  March temperatures relative to 1951-1980 mean, in order from the warmest, were +1.30°C (2016), +1.12°C (2017), +0.92°C (2010), +0.91°C (2002) and +0.90°C (2015).

The figure above compares monthly temperatures in the years 2015-2018.  Note that temperature began rising in the latter part of 2015 as an El Nino was developing.  That late 2015 warming led to record 2016 global heat.  Some ocean models predict that an El Nino may develop later this year, in which case 2019 could be a very hot year.  Historical precedence does not favor the occurrence of two strong El Ninos separated by only 3 years.  On the other hand, the human hand may be altering history.

January-March this year was the 4th warmest on record, but the maps below for the geographical distribution of the temperature anomaly confirm that Europe and the U.S. were not particularly warm.  However, it was nothing like the extreme 2015 cold period in the eastern part of Canada and the U.S., which caused some of the public to doubt the reality of global warming.

pic2.png

To sign up for our monthly update of global temperature (Maps and Graphs), click here.
(http://columbia.us1.list-manage1.com/subscribe…)

Additional figures are on our global temperature web page.
(http://www.columbia.edu/~mhs119/Temperature/)

February 2018 Global Temperature Update

To sign up for our monthly update of global temperature (Maps and Graphs), click here.
Additional figures are on our global temperature web page.

Globally February 2018 was the sixth warmest February since reliable measurements began in 1880, 0.78°C warmer than the 1951-1980 mean.  February temperature was +1.06°C relative to the 1880-1920 base period that provides our best estimate of pre-industrial global temperature.  February temperatures relative to 1951-1980 mean, in order from the warmest, were +1.34°C (2016), +1.12°C (2017), +0.90°C (1998), +0.87°C (2015) and +0.79°C (2010).  A comparison of the monthly mean temperatures for 2015-2018 is shown in the figure above.

febtemp2018.png

As one of the maps above shows, February was cold in Western Europe and Japan, but a large region from Canada to the northern central US was 4-6°C colder than the 1951-1980 mean, while the Arctic region was 8-12°C warmer than normal.  Such cold air outbreaks from the Arctic to middle latitudes, with accompanying movement of warm mid-latitude air into the Arctic, have always occurred because of natural variability of atmospheric wind patterns.  However, there is evidence (Cohen et al., 2018) that the frequency of winter cold air outbreaks from the Arctic has increased as a result of global warming.  Average warming is greater in the Arctic than at lower latitudes, in part because global warming reduces the area of Arctic sea ice, which amplifies the polar warming.  The greater polar warming reduces the temperature gradient between low and high latitudes that drives the mid-latitude jet stream, the west-to-east wind in the upper troposphere.  A weaker jet stream tends to be more “waggly,” increasing the occurrence of Arctic cold air outbreaks.

The situation is different in the Antarctic.  The surface of the Southern Ocean is warming more slowly than most of the planet, in part because of the cooling and freshening effects of increasing ice discharge from Antarctic ice shelves (Hansen et al., 2016).  This cooling effect on the surface of the Southern Ocean competes regionally with the warming effect of increasing greenhouse gases.  There is large year-to-year variability; the strong 2016-17 El Nino caused a decrease of Southern Ocean sea ice over the past two years.  However, if melting of Antarctic ice shelves and ice sheets continues to increase, the warming of the Southern Ocean will continue to be much less than warming in the rest of the world.

Cohen, J., K. Pfeiffer and J.A. Francis, Warm Arctic episodes linked with increased frequency of extreme weather in the United States, Nature Comm., publ. online 13 March 2018.

Hansen, J., M. Sato, P. Hearrty, R. Ruedy, M. Kelley, V. Masson-Delmotte, G. Russell, G. Tselioudis, J. Cao, E. Rignot, I. Velicogna, B. Tormey, B. Donovan, E. Kandiano, K. von Schuckmann, P. Kharecha, A.N. Legrande, M. Bauer, and K. Lo, Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2°C global warming could be dangerous, Atmos. Chen. Phys., 16, 1-52, 2016.

January 2018 Global Temperature Update

January 2018 Global Temperature Update

11.PNG

Globally January 2018 was the fifth warmest January since reliable measurements began in 1880, 0.78°C warmer than the 1951-1980 mean. January temperature was +1.05°C relative to the 1880-1920 base period that provides our best estimate of pre-industrial global temperature. January temperatures relative to 1951-1980 mean, in order from the warmest, were +1.16°C (2016), +0.97°C (2017), +0.95°C (2007) and +0.81°C (2015).

The strong 2015-2016 El Nino ended about a year and half ago and the tropical Pacific is now in a La Nina phase (temperature anomaly less than -0.5°C; see left side of above figure). Because this year is starting in a deep La Nina, 2018 is likely to decline further relative to the past year, but note that 2017 was still 0.1C above the global warming trend line
(http://www.columbia.edu/~jeh1/mailings/2018/20180118_Temperature2017.pdf). Some ocean models are projecting a possible El Nino in the latter part of 2018, which would tend to reverse the recent short-term cooling trend.

The geographical distributions of January temperature for the past four years are shown below.

12.PNG

Global Temperature in 2017

Global Temperature in 2017

18 January 2018

James Hansen[a], Makiko Sato[a], Reto Ruedy[b,c], Gavin A. Schmidt[c], Ken Lo[b,c], Avi Persin[b,c]

 

Abstract.  Global surface temperature in 2017 was the second highest in the period of instrumental measurements in the Goddard Institute for Space Studies (GISS) analysis.  Relative to average temperature for 1880-1920, which we take as an appropriate estimate of “pre-industrial” temperature, 2017 was +1.17°C (~2.1°F) warmer than in the 1880-1920 base period.  The high 2017 temperature, unlike the record 2016 temperature, was obtained without any boost from tropical El Niño warming.

Update of the GISS (Goddard Institute for Space Studies) global temperature analysis (GISTEMP)[1],[2](Fig. 1), finds 2017 to be the second warmest year in the instrumental record.  (More detail is available at http://data.giss.nasa.gov/gistemp/ and http://www.columbia.edu/~mhs119/Temperature; figures here are available from Makiko Sato on the latter web site.)  A few figures are included below as an appendix.

We take 1880-1920 as baseline, i.e., as the zero-point for temperature anomalies, because it is the earliest period with substantial global coverage of instrumental measurements and because it also has a global mean temperature that should approximate “preindustrial” temperature[3].

      We estimate current underlying temperature, excluding short-term variability via linear fit to the post-1970 temperature (Fig. 1).  The result is +1.07°C at the beginning of 2018 relative to 1880-1920.

      Figure 2 compares maps of global temperature anomalies of the past three years.  The map in the lower right is the difference between 2017 and 2015 temperatures, revealing that 2017 was notably warmer than 2015 in the polar regions.  This 2017-2015 difference map suggests the reason why some temperature analyses report 2017 as the third warmest year, behind 2015 as well as 2016.  Some analyses include only area close to the points of actual observations in their ‘global’ analysis.  The GISS analysis[1] extrapolates observations as far as 1200 km from measurement points, thus covering practically the entire globe.  It has been shown, by sampling globally complete data with realistic temporal and spatial variability, that this extrapolation procedure yields a more accurate estimate of annual global temperature than global integration methods that restrict the area to regions very close to observed points.[4],[1]

   Fig. 1.    (a) Global surface temperatures relative to 1880-1920 based on GISTEMP data, which employs GHCN.v3 for meteorological stations, NOAA ERSST.v5 for sea surface temperature, and Antarctic research station data[1].

Fig. 1. (a) Global surface temperatures relative to 1880-1920 based on GISTEMP data, which employs GHCN.v3 for meteorological stations, NOAA ERSST.v5 for sea surface temperature, and Antarctic research station data[1].

   Fig. 2.    Temperature anomalies in 2017, 2016 and 2015 relative to 1951-1980 base period.  The lower right map shows the difference between the 2017 and 2015 maps.  We use the 1951-1980 base period for maps because of more limited global data coverage in 1880-1920.

Fig. 2. Temperature anomalies in 2017, 2016 and 2015 relative to 1951-1980 base period.  The lower right map shows the difference between the 2017 and 2015 maps.  We use the 1951-1980 base period for maps because of more limited global data coverage in 1880-1920.

Figure 3 compares the GISS analysis of global temperature change with the case in which the polar regions, specifically regions poleward of 64 degrees latitude, are excluded from the analysis.  With polar regions excluded, 2017 becomes the third warmest year, and the ‘global’ warming relative to the base period is reduced by almost a tenth of a degree Celsius.  We do not mean to imply that other analyses entirely exclude polar regions.  Therefore we make a more specific test of the impact of omitted regions by carrying out the GISS analysis with local measurements extrapolated only 250 km rather than 1200 km.  Fig. A2 shows that this area limit also causes 2017 to be only the third warmest year.

      We conclude that 2017 probably was the second warmest year.  However, the temperatures of 2015 and 2017 are so close that the difference is unimportant.

      Prospects for continued global temperature change are more interesting and important.  The record 2016 temperature was abetted by the effects of both a strong El Niño and maximum warming from the solar irradiance cycle (Fig. 4).  Because of the ocean thermal inertia and decadal irradiance change, the peak warming and cooling effects of solar maximum and minimum are delayed about two years after irradiance extrema.  The amplitude of the solar irradiance variation is smaller than the planetary energy

   Fig. 3.    Global temperature compared with the result for integration over the region from 64°N to 64°S, which covers 90% of Earth’s surface, excluding only polar regions.

Fig. 3. Global temperature compared with the result for integration over the region from 64°N to 64°S, which covers 90% of Earth’s surface, excluding only polar regions.

  Fig. 4.   Solar irradiance and sunspot number in the era of satellite data.  Left scale is the energy passing through an area perpendicular to Sun-Earth line.  Averaged over Earth’s surface the absorbed solar energy is ~240 W/m2, so the full amplitude of the measured solar variability is ~0.25 W/m2.

Fig. 4.  Solar irradiance and sunspot number in the era of satellite data.  Left scale is the energy passing through an area perpendicular to Sun-Earth line.  Averaged over Earth’s surface the absorbed solar energy is ~240 W/m2, so the full amplitude of the measured solar variability is ~0.25 W/m2.

imbalance, which has grown to about +0.75 ± 0.25 W/m2 over the past several decades due to increasing atmospheric greenhouse gases.[5],[6] However, the solar variability is not negligible in comparison with the energy imbalance that drives global temperature change.  Therefore, because of the combination of the strong 2016 El Niño and the phase of the solar cycle, it is plausible, if not likely, that the next 10 years of global temperature change will leave an impression of a ‘global warming hiatus’.

      On the other hand, the 2017 global temperature remains stubbornly high, well above the trend line (Fig. 1), despite cooler than average temperature in the tropical Pacific Niño 3.4 region (Fig. 5), which usually provides an indication of the tropical Pacific effect on global temperature.[7]  Conceivably this continued temperature excursion above the trend line is not a statistical fluke, but rather is associated with climate forcings and/or feedbacks.  The growth rate of greenhouse gas climate forcing has accelerated in the past decade.[3]  There is also concern that polar climate feedbacks may accelerate.[8]

      Therefore, temperature change during even the next few years is of interest, to determine whether a significant excursion above the trend line is underway.

 

  Fig. 5.    Ni  ñ  o 3.4 and global temperature change during the past five years.

Fig. 5.  Niño 3.4 and global temperature change during the past five years.

Appendix

   Fig. A1.     Global surface temperature relative to 1880-1920 based on GISTEMP data.  (a) Annual and 5-year means since 1880, (b) 12- and 132-month running means since 1970.  Blue squares in (b) are calendar year (Jan-Dec) means used to construct (a).  Update of Fig. 2 in reference 3.

Fig. A1.  Global surface temperature relative to 1880-1920 based on GISTEMP data.  (a) Annual and 5-year means since 1880, (b) 12- and 132-month running means since 1970.  Blue squares in (b) are calendar year (Jan-Dec) means used to construct (a).  Update of Fig. 2 in reference 3.

  Fig. A2.   Global surface temperature with extrapolation of data limited to 250 km from observations.

Fig. A2.  Global surface temperature with extrapolation of data limited to 250 km from observations.

  Fig. A3.   Global temperature in the past 100 and past 50 years based on local linear trends. 

Fig. A3.  Global temperature in the past 100 and past 50 years based on local linear trends. 

References

[a] Earth Institute, Columbia University, New York, NY

[b] SciSpace LLC, New York, NY

[c] NASA Goddard Institute for Space Studies, New York, NY

[1] Hansen, J., R. Ruedy, M. Sato, and K. Lo, 2010: Global surface temperature change. Rev. Geophys., 48, RG4004, doi:10.1029/2010RG000345.

[2] The current GISS analysis employs NOAA ERSST.v5 for sea surface temperature, GHCN.v.3.3.0 for meteorological stations, and Antarctic research station data, as described in reference 1.

[3] Hansen, J., M. Sato, P. Kharecha, K. von Schuckmann, D.J. Beerling, J. Cao, S. Marcott, V. Masson-Delmotte, M.J. Prather, E.J. Rohling, J. Shakun, P. Smith, A. Lacis, G. Russell, and R. Ruedy, 2017: Young people's burden: Requirement of negative CO2 emissions. Earth Syst. Dynam., 8, 577-616, doi:10.5194/esd-8-577-2017.

[4] Hansen, J.E., and S. Lebedeff, 1987: Global trends of measured surface air temperature. J. Geophys. Res., 92, 13345-13372, doi:10.1029/JD092iD11p13345.

[5] von Schuckmann, K., M.D. Palmer, K.E. Trenberth, A. Cazenave, D. Chambers, N. Champollion, J. Hansen, S.A. Josey, N. Loeb, P.-P. Mathieu, B. Meyssignac, M. Wild, 2016: An imperative to monitor Earth's energy imbalance Nature Climate Change 6, 138-144, doi:10.1038/nclimate2876.

[6] Hansen, J., M. Sato, P. Kharecha, and K. von Schuckmann, 2011: Earth's energy imbalance and implications. Atmos. Chem. Phys., 11, 13421-13449, doi:10.5194/acp-11-13421-2011.

[7] Philander, S.G., Our Affair with El Niño: How We Transformed an Enchanting Peruvian Current into a Global Climate Hazard, Princeton Univ. Press, Princeton, NJ, 288 pp., 2006.

[8] Sommerkorn, M. and Hassol, S.J., 2009: Arctic Climate Feedbacks: Global Implications, World Wildlife Fund report, 98 pages, based on Sommerkorn M., Hamilton N. (eds.) 2008. Arctic Climate Impact Science – an update since ACIA. http://assets.panda.org/downloads/arctic_climate_impact_science_1.pdf

 

November 2017 Global Temperature Update

November 2017 Global Temperature Update

1.PNG

Globally November 2017 was the third warmest November since reliable measurements began in 1880, 0.87°C warmer than the 1951-1980 mean. November temperature was +1.15°C relative to the 1880-1920 base period that provides our best estimate of pre-industrial global temperature.
The warmest November was 2015 at +1.03°C relative to the 1951-1980 mean. 2016 had the 2nd
warmest November at +0.90°C.

The strong 2015-2016 El Nino ended about a year and half ago and the tropical Pacific is now in a La Nina phase (temperature anomaly less than -0.5°C; see left side of above figure). However, global temperature remains high, which will make 2017 the 2nd warmest year globally.

The geographical distribution of annual temperature anomalies for the past three years is shown in the figure below (January-November mean for 2017).

2.PNG

October Global Temperature Update

October Global Temperature Update

To sign up for our monthly update of global temperature (Maps and Graphs), click here.

Additional figures are on our global temperature web page.

 

Oct2017-620x419.png

Globally October 2017 was the second warmest October since reliable measurements began in 1880, 0.90C warmer than the 1951-1980 mean.  October temperature was +1.18C relative to the 1880-1920 base period, which provides our best estimate of pre-industrial global temperature.  The warmest October was 2015 at +1.08C relative to the 1951-1980 mean.  2016 was the 3rd warmest at +0.89C.  The 2017 January to October 10-month mean is second highest, behind 2016, compared to the first 10 months of other years.

Although a weak La Nina is present, the global mean temperature in October stayed relatively high; polar regions were especially warm.  2017 will likely to be the second warmest year in the record.

September 2017 Global Temperature Update

September 2017 Global Temperature Update

To sign up for our monthly update of global temperature (Maps and Graphs), click here.

Additional figures are on our global temperature web page.

 

image-sept 2017.png

Globally September 2017 was the fourth warmest September since reliable measurements began in 1880, 0.80C warmer than the 1951-1980 mean.  Warmest Septembers were 2014 and 2016 at +0.87C, with 2015 third at 0.82C.

The 2017 January to September 9-month mean is second highest, behind 2016, compared to the first nine months of other years, as shown above.

If the temperature anomaly for the next three months (relative to the 1951-1980 mean) is less than 0.75C (i.e., if October-December 2017 is more than 0.33C cooler than October-December 2015) the annual 2017 temperature would fall below that of 2015, making 2017 the third warmest year.  Even though a La Nina may be in the offing for this fall-winter, a cooling that large seems unlikely, so 2017 will probably be the second warmest year.

August 2017 Global Temperature Update

August 2017 Global Temperature Update

To sign up for our monthly update of global temperature (Maps and Graphs), click here.

Additional figures are on our global temperature web page.

global-surface-temp-aug.png

Globally August 2017 was the second warmest August since reliable measurements started in 1880, 0.85C warmer than the 1951-1980 mean.  The warmest August was in 2016 at +0.99C.  (See the figure above.)

Compared to the 1880-1920 mean (which is also our best estimate for the pre-industrial average temperature) global temperature is now about +1.2C (see figure below).  The warming rate since 1970 is 0.17C/decade.

Aug2017.png

July 2017 Global Temperature Update

July 2017 Global Temperature Update

To sign up for our monthly update of global temperature (Maps and Graphs), click here.

Additional figures are on our global temperature web page.

global-surface-temp.png

The GISS global temperature analysis now uses NOAA’s newest Sea Surface Temperature version, ERSSTv5, which has improved spatial and temporal variability.  The effect on global temperature of the change from ERSSTv4 to v5 is small compared to the uncertainty in the temperature change itself (above figure).  For more detailed comparisons please see http://www.columbia.edu/~mhs119/Temperature/ERSSTv5vsv4/

Globally July 2017 was the warmest July (+0.83C relative to the 1951-1980 mean) in the record, with July 2016 second at +0.82C.  See figure below.

jan-july-mean-surface-temp.png

June Global Temperature Update

June Global Temperature Update

To sign up for our monthly update of global temperature (Maps and Graphs), click here.

Additional figures are on our global temperature web page.

jan-june.png

For the half year January-June, 2017 is the second warmest, about halfway between the warmest (2016) and the 3rd warmest (2015).

Global temperature dropped sharply between May and June this year, as shown by the red curve in the lower right part of the first chart.  That sharp drop is also apparent in the line graph in the second chart, where, for the first time since 2014, the monthly temperature anomaly dropped well below the trend line.

The map for the June 2017 temperature anomaly (right side of the second chart) reveals that the sharp drop in global temperature was due substantially to an unusually cold Antarctica*.  Antarctic temperature in winter months has very large natural variability, so there is no reason to expect that cold anomaly in Antarctica to continue.

However, returning to the line graphs in the lower right of Chart 1, we note that it is unlikely that the second half of 2017 can match the warmth of the second half of 2015.  The second half of 2015 was affected by a building strong El Nino.  In contrast projection, NOAA projections for the second half of 2017 (chart 25 of http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf) have declining SSTs in the tropical Pacific.  So it is possible that the 2017 annual mean temperature may fall closer to the 2015 annual mean.

surface-temp.png

*Note that the rectangular latitude-longitude projection of our maps exaggerates the size of polar anomalies.  Other projections can reduce or remove area bias.  We prefer the rectangular projection because it allows more accurate location of features.  Compressing polar regions in alternative projections produces lots of blank area on the page and loses spatial resolution in the polar region.

May Global Temperature Update

May Global Temperature Update

To sign up for our monthly update of global temperature (Maps and Graphs), click here.

Additional figures are on our global temperature web page.

May 2017, at +0.88C relative to the 1951-1980 mean, was the second warmest Mayin the period of instrumental data, only 0.05C cooler than May 2016 record high (0.93C).

ENSO (El Nino-Southern Oscillation) in the tropical Pacific are now near neutral, while the first half of 2016 was affected by the strong 2015-2016 El Nino.  Given present and projected ENSO conditions (neutral or slightly positive) it can be projected that 2017 as a whole is likely to be the second warmest year in the instrumental record, not much cooler than 2016.

Note: our “Young People’s Burden” paper has been accepted for publication in Earth System Dynamics.  We thank the editor and reviewers for assistance in producing a much improved version of the paper, which we will make available with discussion on www.columbia.edu/~jeh1 as soon as it is published (within a few weeks).

surf-temp-may.png

April Global Temperature Update

April Global Temperature Update

To sign up for our monthly update of global temperature (Maps and Graphs), click here.

Additional figures are on our global temperature web page.

Almost a year after the strong 2015-2016 El Nino, global mean temperature remains well above the pre-El Nino level.  Global temperature with short-term variability removed has been rising about 0.18C per decades since 1970.  Warming of 1.5C above the 1880-1920 mean will be reached in the early 2040s if this rate is maintained.

The immediate drive for this warming is the planetary energy imbalance.  Warming by itself would reduce the imbalance and the warming rate, but continued growth of greenhouse gases maintains the imbalance and the rapid warming rate.

T_1880-1920base_2parts-2.png

March Global Temperature Update

March Global Temperature Update

To sign up for our monthly update of global temperature (Maps and Graphs), click here.

Additional figures are on our global temperature web page.

The first three months of 2017 are the 2nd warmest January-March in the instrumental record, about half way between 2016 (warmest) and 2015 (2nd warmest annual mean, 3rd warmest January-March).

Note that most of the monthly records were set in 2016.

jan-march-STA.png

February 2017 Global Temperature Update

feb-2017-620x223.png

Global temperature declined during 2016, with global temperature lagging Nino3.4 temperature by a few months (Fig. 1), as usual.  However, temperature in January and February 2017 was unusually high, Jan-Feb 2017 being the second warmest Jan-Feb (after 2016).

Although the tropical SST has been in ENSO (El Nino Southern Oscillation) neutral conditions for the past several months (i.e., Nino3.4 between -0.5C and +0.5C), Nino3.4 temperature has begun to rise, indicating likely return to at least a weak El Nino in 2017.  Given the warming tropics and the low sea ice cover in both hemispheres, we infer that 2017 will be another unusually warm year, extending long-term global warming trends.

Globally both February 2017 and Northern Hemisphere winter were the second warmest since reliable measurements started in 1880 (Fig. 2).  In February the Eastern U.S. and a part of Siberia were extremely warm.

Feb2017DJF2017_globUS.png

Global Temperature in 2016

Global Temperature in 2016

18 January 2017

James Hansen[1], Makiko Satoa, Reto Ruedy[2],[3] Gavin A. Schmidtc, Ken Lob,c, Avi Persinb,c

Abstract.  Global surface temperature in 2016 was the highest in the period of instrumental measurements.  Relative to average temperature for 1880-1920, which we take as an appropriate estimate of “pre-industrial” temperature, 2016 was +1.26°C (~2.3°F) warmer than in the base period.  The 2016 temperature was partially boosted by a 2015-16 El Niño, which was almost as strong as the 1997-98 “El Niño of the century”.  We estimate current global temperature excluding short-term variability as +1.07°C relative to 1880-1920, based on linear fit to post-1970 global temperatures.

Update of the GISS (Goddard Institute for Space Studies) global temperature analysis (GISTEMP)[i],[ii] (Fig. 1a), finds 2016 to be the warmest year in the instrumental record.  (More detail is available at http://data.giss.nasa.gov/gistemp/ and http://www.columbia.edu/~mhs119/Temperature; figures in this summary are available from Makiko Sato on the latter web site.)  For the second year in a row the prior record was broken by a substantial margin.  2015 and 2016 annual temperatures were, in part, boosted by the 2015-16 El Niño.  Because of the delayed global response to the natural El Niño/La Niña variability,[iii] it is likely that the 2017 global temperature will fall below that of 2016, as discussed below.

Here we choose 1880-1920 as baseline, i.e., as the zero-point for temperature anomalies, because it is the earliest period with substantial global coverage of instrumental measurements and because it also has a global mean temperature that should approximate “preindustrial” temperature[iv].  The United Nations Framework Convention[v] and Paris Agreement[vi] define goals relative to “preindustrial”, but do not define that period.  Although human-caused increases of greenhouse gases (GHGs) by 1880-1920 were already sufficient to cause a small warming,[vii] 1880-1920 was also marked by above-average volcanic aerosols[viii], which have a cooling effect.  Extreme Little Ice Age conditions may have been ~0.1C cooler than the 1880-1920 mean,[ix] but the Little Ice Age seems inappropriate to define preindustrial temperature because the deep ocean did not have time to reach equilibrium with brief surface conditions.  Choosing a

  Fig. 1.  (a) Global surface temperatures relative to 1880-1920 based on GISTEMP data, which employs GHCN.v3 for meteorological stations, NOAA ERSST.v4 for sea surface temperature, and Antarctic research station data1.  (b) Post-1970 linear fit to 132-month (11-year) running mean is added to the results shown in (a).

Fig. 1. (a) Global surface temperatures relative to 1880-1920 based on GISTEMP data, which employs GHCN.v3 for meteorological stations, NOAA ERSST.v4 for sea surface temperature, and Antarctic research station data1.  (b) Post-1970 linear fit to 132-month (11-year) running mean is added to the results shown in (a).

  Fig. 2.  Temperature anomalies in 2016 relative to 1880-1920 base period.

Fig. 2. Temperature anomalies in 2016 relative to 1880-1920 base period.

preindustrial global temperature thus has uncertainty of at least 0.1°C, but 1880-1920 temperature seems about right and that period has the merit of near-global data.  An alternative choice of 1720-1800 as base period has similar (within ~0.1°C) global temperature as 1880-1920[x], and their analysis10 and ours both reach the +1°C level in 2014-2015.

We estimate current underlying temperature, excluding short-term variability via linear fit to the post-1970 temperature (Fig. 1b).  The result is +1.07°C at the end of 2016 relative to 1880-1920.

A global map of 2016 surface temperature anomalies relative to 1880-1920 is shown in Fig. 2.  Maps for each of the last four years (Fig. 3) are relative to the 1951-1980 base period to allow more complete global coverage.  2013 is the sixth warmest year in the GISS analysis, 2014, 2015, and 2016 are the third, second and first warmest, respectively.  The tropical warming in the past few years is apparent, and especially the warming in the Arctic.

  Fig. 3.  Temperature anomalies in the last four years.

Fig. 3. Temperature anomalies in the last four years.

  Fig. 4.  (a) Temperature anomalies in Niño3.4 region3, (b) for the global mean, and (c) for the globe excluding the Arctic (latitudes above 66°N).  In each case the temperature is detrended by subtracting the temperature based on the linear change over 1970-2016.  Data source for (a)  http://www.cpc.ncep.noaa.gov/data/indices/ersst4.nino.mth.81-10.ascii

Fig. 4. (a) Temperature anomalies in Niño3.4 region3, (b) for the global mean, and (c) for the globe excluding the Arctic (latitudes above 66°N).  In each case the temperature is detrended by subtracting the temperature based on the linear change over 1970-2016.  Data source for (a) http://www.cpc.ncep.noaa.gov/data/indices/ersst4.nino.mth.81-10.ascii

  Fig. 5.  Observed Niño3.4 temperature and projections with the NOAA NCEP CFS.v2 forecast model (http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml#discussion).

Fig. 5. Observed Niño3.4 temperature and projections with the NOAA NCEP CFS.v2 forecast model (http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml#discussion).

  Fig. 6.  Zonal-mean temperature for different latitude bands.  (a) 132-month (11-year) running means for all five regions, (b-d) 12-month running means.  All results are relative to the 1880-1920 base period.

Fig. 6. Zonal-mean temperature for different latitude bands.  (a) 132-month (11-year) running means for all five regions, (b-d) 12-month running means.  All results are relative to the 1880-1920 base period.

The 2015-16 El Niño was weaker than the 1997-98 El Niño, as measured by the peak SST anomaly in the Niño3.4 region, but the recent El Niño was longer lasting (Fig. 4a).  The longevity of tropical warmth may have contributed to the magnitude of global warming, which was larger for the recent El Niño (Fig. 4b).  The most extreme warming was in the Arctic (Figs. 2 and 3); when the Arctic is excluded from the global average, global warming relative to the trend line is slightly larger in 1998 than in 2016 (Fig. 4c).

The 12-month running mean temperature peaked at 1.31°C and declined to 1.26°C by the end of 2016 (Fig. 1), with global peak temperature lagging the Niño3.4 temperature peak by 4 months (monthly mean global temperature maximum lags monthly Niño3.4 by 3 months, while the lag is 5 months for 12-month running means).  This lag, similar to that for the 1997-98 El Niño, is as expected as maximum correlation

of global and Niño3.4 temperatures has global temperature lagging by 4 months1,[xi].  Global temperature in 2017 will almost surely fall from the 2016 value, as it has after other strong El Niños, but the drop may not be as steep as it was in 1999.  The 1997-98 El Niño was followed by a strong La Niña (Fig. 4a), but temperature in the Niño3.4 region in 2016 barely reached the −0.5°C level, has since returned to Niño-neutral conditions, and is projected to remain Niño-neutral for the next several months (Fig. 5).

Warming in the Arctic is now about 3°C, and in the tropics about 1°C relative to 1880-1920 (Fig. 6).  Middle latitude warming is larger in the Northern Hemisphere than in the Southern Hemisphere, as expected, because of the much larger proportion of land in the Northern Hemisphere.  Warming over global land area in the past century is about twice as large as warming over the global ocean (Fig. 7), which is consistent with expectations based on global climate modeling[xii].

  Fig. 7.  Global land and global ocean surface temperature anomalies.  Light lines are 12-month running means and heavy lines are 132-month (11-year) running means.

Fig. 7. Global land and global ocean surface temperature anomalies.  Light lines are 12-month running means and heavy lines are 132-month (11-year) running means.

  Fig. 8.  Daily temperatures in Central Park, New York City, during 2015.  Data source: NOAA National Weather Service New York Office  http://w2.weather.gov/climate/index.php?wfo=okx

Fig. 8. Daily temperatures in Central Park, New York City, during 2015.  Data source: NOAA National Weather Service New York Office http://w2.weather.gov/climate/index.php?wfo=okx

Reminder of the large magnitude of local temperature variability, relative to global mean warming, is always in order.  We use data for New York City to illustrate (Fig. 8).  Local annual mean temperature now has high likelihood of being warmer than mean climatology (Fig. 8a), but few people are concerned with annual mean temperature.  Monthly temperature anomalies (Fig. 8b) are more noticeable to the public, but in this case the long-term average warming of about 1°C is much smaller than the interannual variability of monthly mean temperature.  Although the past six Decembers have all been warmer than the 1951-1980 average, the interannual variability is so large that some months colder than the climatological mean must be anticipated.  Daily temperature anomalies are even larger (Fig. 8c).  One day in February 2016 the temperature reached a low of −1°F (−18°C), which was 28°F (16°C) colder than climatology.

 

References

[1] Earth Institute, Columbia University, New York, NY

[2] Trinnovim LLC, New York, NY

[3] NASA Goddard Institute for Space Studies, New York, NY

[i] Hansen, J., R. Ruedy, M. Sato, and K. Lo, 2010: Global surface temperature change. Rev. Geophys., 48, RG4004, doi:10.1029/2010RG000345.

[ii] The current GISS analysis employs NOAA ERSST.v4 for sea surface temperature, GHCN.v.3.3.0 for meteorological stations, and Antarctic research station data, as described in reference 1.

[iii] Philander, S.G., Our Affair with El Niño: How We Transformed an Enchanting Peruvian Current into a Global Climate Hazard, Princeton Univ. Press, Princeton, NJ, 288 pp., 2006.

[iv] The United Nations 1992 Framework Convention on Climate Change (UNFCCC, 1992) stated its objective as ‘…stabilization of GHG concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system’.  The 15th Conference of the Parties (Copenhagen Accord, 2009) concluded that this objective required a goal to ‘…reduce global emissions so as to hold the increase of global temperature below 2°C…’.  The 21st Conference of the Parties (Paris Agreement, 2015) strengthened this objective ‘to holding the increase of global average temperature to well below 2°C above preindustrial levels and to pursue efforts to limit the temperature increase to 1.5°C above preindustrial levels…’.

[v] United Nations: Framework Convention on Climate Change (UNFCCC), United Nations, New York, NY, available at: http: //unfccc.int/essential_background/items/6036.php (last access: 3 March 2016), 1992.

[vi] Paris Agreement 2015, UNFCCC secretariat, available at “Paris Agreement, FCCC/CP/2015/L.9/Rev.1” (PDF), 12 December 2015.

[vii] Myhre, G., Shindell, D., Breon, F., Collins, W., Fuglestvedt, J., Huang, J., Koch, D., Lamarque, J. F., Lee, D., Mendoza, B., Nakajima, T., Robock, A., Stephens, G., Takemura, T., and Zhang, H: Anthropogenic and natural climate forcing, in: Climate Change 2013: The Physical Science Basis, edited by: Stocker, T. F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S. K., Boschung, J., Nauels, A., Xia, Y., Bex, V., and Midgley, P. M., Cambridge University Press, Cambridge, United Kingdom, 2013.

[viii] Sato, M., Hansen, J. E., McCormick, M. P., and Pollack, J. B.: Stratospheric aerosol optical depths, 1850-1990, J. Geophys. Res., 98, 22987-22994, doi:10.1029/93JD02553, 1993.

[ix] Abram, N. J., McGregor, H. V., Tierney, J. E., Evans, M. N., McKay, N. P., Kaufman, D. S., and PAGES 2k Consortium: Early onset of industrial-era warming across the oceans and continents, Nature, doi:10.1038/nature19082, 2016.

[x] Hawkins, E., Ortega, P., Suckling, E., Schurer, A., Hegerl, G., Jones, P., Joshi, M., Osborn, T.J., Masson-Delmotte, V., Mignot, J., Thorne, P., and van Oldenborgh, G.J.: Estimating changes in global temperature since the pre-industrial period, Bull. Amer. Meteorol. Soc., in press, 2017.

[xi] Foster, G., Annan, J.D., Jones, P.D., Mann, M.E., Mullan, B., Renwick, J., Salinger, J., Schmidt, G.A., and Trenberth, K.E.: Comment on “Influence of the Southern Oscillation on Tropospheric Temperature” by J.D. McLean, C.R. de Freitas, and R.M. Carter, J. Geophys. Res., 115, D09110, doi:10.1029/2009JD012960, 2010.

[xii] Collins, M., Knutti, R., Arblaster, J., Dufresne, J. L., Fichefet, T., Friedlingstein, P., Gao, X., Gutowski, W. J., Johns, T., Krinner, G., Shongwe, M., Tebaldi, C., Weaver, A., and Wehner, M.: Long-term climate change: Projections, commitments and irreversibility, in: Climate Change 2013: The Physical Basis, edited by: Stocker, T. F., Qin, D., Plattner, G.-K., Tignor, M., Allen, S. K., Boschung, J., Nauels, A., Xia, Y., Bex, V., and Midgley, P. M., Cambridge University Press, Cambridge, United Kingdom, 2013.

January 2017 Global Temperature Update

jan-2017.png

Global temperature declined during 2016 (Fig. 1) as the strong 2015-16 El Nino peaked in late 2015.  As usual, global temperature peaked a few months after the Nino3.4 maximum.

Nino3.4 temperature is now near the boundary (-0.5C) between La Nina and Nino-neutral conditions, with most models predicting a moderate rise in tropical temperatures over the next several months.

Despite the relatively cool tropical Pacific region, global temperature has not declined all the way to the pre-El Nino level, at least in part because of the unusual Arctic warmth (Fig. 2).

2017-jan.png