April 2019 Global Temperature Update

April 2019 Global Temperature Update

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April 2019 was 2nd warmest April in the 140-year instrumental record at +0.99°C relative to 1951-1980 (2016 was +1.07°C).  So far 2019 is the 3rd warmest year (right graph), but residual global warming (which lags Niño3.4 several months) from the weak El Niño may make 2019 the 2nd warmest year.

NCEP (NOAA) forecast for the temperature in the Niño3.4 region (green range below), as provided at https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf, still has a huge range for the El Niño strength the rest of the year – ranging from growth to a moderately strong El Niño to rapid phasedown to La Niña.  Is the tropical ocean really THAT unpredictable?

Mark Cane once told us that Nature rolls the El Niño dice in Northern Hemisphere spring, determining El Niño status for the year.  It’s spring.  Presumably the range of the forecasts will narrow soon.  If not, hopes for something much better than nowcasting (looking out the window) seem to have been dashed, contrary to the great expectations of a few decades ago.  Does a good review of the El Niño forecasting situation, preferably in lay language, exist?

The 12-month running-mean of global temperature (dark blue curve in lower right graph) now has a defined minimum in mid-2018, lagging the January 2018 Niño3.4 minimum by several months, as expected.

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March 2019 Global Temperature Update

March 2019 Global Temperature Update

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March 2019 was the 3rd warmest March in the 140-year instrumental record, at +1.11°C relative to the 1951-1980 mean (2016 was +1.31°C, 2017 was +1.13°C).  Tell that to people in the Northern and Midwestern United States, regions hit by brutal cold and heavy snow! 

The map of temperature anomalies shows regions in the Arctic that were more than 10°C (about 20°F) above normal (1951-1980 mean) on monthly average!  Such Arctic warmth is not from local heating; it is warm air from lower latitudes.  Of course, the imported air is balanced by Arctic air moving out – the 48 United States being the recipient in this case.

Polar amplification of global warming causes the jet stream to be less tightly wound, which may increase the chance of cold air outbreaks to middle latitudes.  However, March, as the transition month from winter to warmer seasons, always has highly variable weather, as shown by the maps below for the last six years.  And Jonathan Erdman of weather.com argues that March is mainly a winter month.

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A PDF of this Temperature Update is available here.

February 2019 Global Temperature Update

February 2019 Global Temperature Update

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Global temperature in February 2019 (at +0.92°C relative to 1951-1980 base period) was third warmest February in the 140-year record since 1880.  Warmest Februarys were 2016 (+1.34°C) and 2017 (+1.12°C).   February temperature anomalies cover a huge range, as much as 6-8°C colder than the 1951-1980 mean in much of western Canada and the northwest and north central U.S., and as much as 8-12°C warmer than 1951-1980 in parts of northern Eurasia, and Alaska and the surrounding Arctic.

NCEP forecast given by NOAA (indicated by the green range below) as provided at https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf on March 18 has a large range for the strength of the El Nino predicted for this year.  It will be interesting to compare the development over the next few months of 2019 with the same months in 2015.  If the 2019 El Nino is strong, it could presage a very high global temperature in 2020.

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A PDF of this Temperature Update is available here.

January 2019 Global Temperature Update

January 2019 Global Temperature Update

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Global temperature in January 2019 (at +0.88°C relative to 1951-1980 base period) was the fourth warmest January in the 140-year record since 1880.  The warmest Januarys were 2016 (+1.15°C), 2017 (+0.97°C) and 2007 (+0.94°C).

Northeastern Canada was unusually cool (as much as 3.6°C below the 1951-1980 mean), but areas in Siberia and northwestern Canada were more than +5°C above normal, where ‘normal’ is defined as the 1951-1980 mean.  Australia experienced a scorching summer, most of the country at least +3°C above normal.  The global temperature pattern is typical of El Ninos (See maps on http://www.columbia.edu/~mhs119/ElNino-LaNina/), despite the current El Nino being very weak.

Almost the entire United States was warmer than normal, averaged over the month.  Of course the monthly mean can hide extreme cold spells that cause people to wonder where “global warming” has gone, when it has not gone anywhere.  Some recent cold weather may even be unusually cold, because of behavior of the Arctic vortex, as noted in prior temperature updates.  Examples of cold weather are shown on the right in the figure below.  The daily data are from NOAA https://w2.weather.gov/climate/index.php?wfo=okx and https://w2.weather.gov/climate/index.php?wfo=mpx .

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A PDF of this temperature update is available here.

Global Temperature in 2018 and Beyond

Global Temperature in 2018 and Beyond

06 February 2019

James Hansen[1], Makiko Sato[1], Reto Ruedy[2],[3], Gavin A. Schmidt[3], Ken Lo[2],[3]

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

[2] SciSpace LLC, New York, NY

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

Abstract.  Global surface temperature in 2018 was the 4th highest in the period of instrumental measurements in the Goddard Institute for Space Studies (GISS) analysis.  The 2018 global temperature was +1.1°C (~2°F) warmer than in the 1880-1920 base period; we take that base period as an estimate of ‘pre-industrial’ temperature.  The four warmest years in the GISS record all occur in the past four years, and the 10 warmest years are all in the 21st century.  We also discuss the prospects for near-term global temperature change.

Access the full version and continue reading in PDF: http://www.columbia.edu/~jeh1/mailings/2019/20190206_Temperature2018.pdf

Figures of this Communication are available:

http://www.columbia.edu/~mhs119/Temperature/Temp2018_figures/

Annual Global Temperature Rankings available:

http://www.columbia.edu/~mhs119/Temperature/

November 2018 Global Temperature Update

November 2018 Global Temperature Update

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November 2018 global temperature, at 0.77°C relative to the 1951-1980 base period, tied with 2010 as the fifth warmest November since reliable data began in 1880.  Most people, however, care more about the temperature where they live.  For people in North America, except those on the West Coast, November was cold (see map).

Does the cold November in North America portend a cold winter?  Curiously, Northern Hemisphere temperature patterns were nearly identical in 2014 and 2018.  So let’s look at the months that followed in 2014 (maps below).  December and January were unusually warm in 2015, but wham, frigid air arrived for February (we remember)!

Middle and high latitude winter climate is notoriously noisy (variable).  However, we know that a moderate El Nino has begun.  This knowledge increases the odds of making a good forecast.  El Nino winters are commonly, but not always, marked by higher than normal temperature stretching from Alaska in a southeasterly direction across the Canadian/U.S. border into the middle U.S., but not always reaching all the way to the Southeast U.S.

So, considering also the effects of global warming, if you are a betting person (we are not) you would have an excellent chance of being right if you bet that the winter as a whole in the U.S. is going to be warmer than normal (1951-1980) climatology.  But month-to-month?  Make your own guess.

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A PDF of this temperature update is available: http://www.columbia.edu/~mhs119/Temperature/Emails/November2018.pdf

October 2018 Global Temperature Update

October 2018 Global Temperature Update

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October 2018 was the second warmest October since 1880.  At +0.99°C (relative to 1951-1980) it trailed only October 2015 (+1.08°C).

Extreme regional temperature anomalies in the Northern Hemisphere (see map), as much as +6-8°C in Siberia and minus 2-3°C in North America were evidently related to a wind anomaly carrying warm air in a northeasterly direction across Asia, with the balancing flow bringing Arctic air into North America.

Global temperature is beginning to rise as the tropical Pacific is in the early phase of an El Niño, only three years after the prior one.  It will be interesting to compare global temperature in coming months with 2015-16 temperatures (blue curve in the above figure for the rest of this year, then the green curve).

The record 2016 global temperature got a maximum boost from the Sun as 2016 was 1-2 years after Solar Maximum (link to http://www.columbia.edu/~mhs119/Solar/).  In contrast, 2019 will be during a deep Solar Minimum.

The record 2016 global temperature was boosted mainly by a ‘Super El Niño’, at least as judged by the usual Niño3.4 index, which matched or exceeded the 3.4 index for the 1997 Super El Niño.  We note, however, that recent high 3.4 indices (the 3.4 index is the temperature anomaly in a small region in the tropical Pacific) may be partly a result of a background global warming trend.

So it will also be interesting to see how strong this El Niño will be.  It may be that apparent El Niño strengths are boosted by global warming.

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September 2018 Global Temperature Update

September 2018 Global Temperature Update

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September 2018 global temperature, at 0.75°C relative to the 1951-1980 base period, was the sixth warmest September (tied with 2005) since reliable measurements began in 1880, with some very warm and very cold areas in the northern high latitudes (left side of the figure on the top).  Most of Europe and the U.S. were 1-3°C warmer than the 1951-1980 mean.  Warmer Septembers occurred in 2014 and 2016 (+0.88°C), 2015 (+0.82°C), 2013 (+0.77°C) and 2017 (+0.76°C).  January through September means were, from the warmest, 2016 (1.03°C), 2017 (0.91°C), 2018 (0.81°C) and 2015 (0.80°C).  2018 seems likely to end up as the fourth warmest year since 1880.

For the base period 1880-1920, which provides our best estimate of pre-industrial temperature, the September 2018 anomaly was 1.02°C.  Models predict an El Nino to begin in the next few months, and the tropical Pacific has begun to warm.  We conclude that global temperature has reached a level of at least 1°C relative to pre-industrial climate even in the presence of La Nina cooling.

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Global Warming and East Coast Hurricanes

Global Warming and East Coast Hurricanes

17 September 2018

James Hansen and Makiko Sato

This Communication is also our Monthly Temperature Update for August 2018. Monthly temperature updates are available from either web page (Hansen or Sato) or directly here.

Maps below show the temperature anomaly for the past three months and the seasonal mean (Northern Hemisphere Summer). We draw attention to the cool region southeast of Greenland and warmth in the middle of the North Atlantic.

Wally Broecker suggested decades ago that freshwater injection onto the North Atlantic could cause shutdown of the overturning ocean circulation (AMOC, Atlantic Meridional Overturning Circulation). Rahmstorf et al. (2015)[1] present evidence that a 20th century trend toward the cooling southeast of Greenland was due to a slowdown of AMOC, linking the trend to observed freshening of the North Atlantic surface water that may have been due to some combination of anomalous sea ice export from the Arctic, Greenland melt, and increased precipitation and river runoff.

In our paper on ice melt, sea level rise and superstorms[2] we conclude from multiple lines of evidence that a 21st century slowdown of AMOC is underway. Ocean surface temperature response to AMOC slowdown, in addition to cooling southeast of Greenland, includes warming off the U.S. East Coast, a temperature pattern emerging from high ocean resolution simulations (Saba et al., 2015)[3] .

So, does global warming have a hand in the magnitude of the Hurricane Florence disaster on the U.S. East Coast? Yes, we can say with confidence, it contributes in several ways.

First, there is the fact that sea level rise due to global warming is already well over a foot along the U.S. East Coast. Ice melt due to global warming accounts for about 20 cm (8 inches) global average sea level rise (Fig. 29 in our Ice Melt paper[2]). Slowdown of the Gulf Stream, which is a part of the AMOC slowdown, adds to East Coast sea level. The slowdown reduces the west-to-east upward slope of the ocean surface across the Gulf Stream[4] , causing piling up of water on the East Coast. The combined sea level rise from these effects, which is also responsible for “sunny day flooding” on the Eastern Seaboard, makes hurricane storm surges greater.

Figure 1. Surface temperature anomalies for the past three months.

Figure 1. Surface temperature anomalies for the past three months.

Second, the warmer ocean surface and atmosphere result in greater rainfall amounts. Of course the primary reason for extraordinary rainfall amounts from Florence was the storm’s slow movement.

Third, warmer ocean surface provides more fuel for tropical storms and expands the ocean area able to generate and maintain these storms. Part of a given hurricane’s strength can be attributed to such extra warming of the ocean surface. That effect was pronounced in the case of Hurricane Sandy, which maintained hurricane wind speeds all the way to New York City because of the unusually warm sea surface off the United States East Coast.

What about the track of Florence and the fact that it stalled, resulting in huge local rainfall totals? The track and speed of a given hurricane depend on large scale mid-latitude weather patterns that are largely a matter of chance. As the area in which “tropical” storms can form expands poleward, the opportunity for a mid-latitude high pressure system to push a storm westward may increase, but we are unaware of specific studies. What we can say is that historical hurricane tracks may not be an accurate picture of future tracks.

The number of hurricanes striking the continental U.S. does not show a notable trend (Fig. 2). Indeed, the current decade has only the rest of this year and next year to add to its total to avoid being the decade with the smallest number of hurricanes hitting the continental United States. This small reduction in landfalls seems to be a matter of chance[5]. Damage per hurricane is more important. Global warming already has a large impact on damage for reasons given above. Those impacts, especially those arising from increasing sea level, may accelerate exponentially, if high fossil fuel emissions continue[2].

Fig. 2. The three category 5 hurricanes to strike the U.S. were: Labor Day (Sept. 1935, SW FL, 892 hPa, 184 mph), Camille (Aug 1969, LA & MS, 909 hPa), Andrew (Aug 1992, SE FL, 922 hPa, 167 mph); source: http://www.aoml.noaa.gov/hrd/hurdat/All_U.S._Hurricanes.html.

Fig. 2. The three category 5 hurricanes to strike the U.S. were: Labor Day (Sept. 1935, SW FL, 892 hPa, 184 mph), Camille (Aug 1969, LA & MS, 909 hPa), Andrew (Aug 1992, SE FL, 922 hPa, 167 mph); source: http://www.aoml.noaa.gov/hrd/hurdat/All_U.S._Hurricanes.html.

 

[1] Rahmstorf, S., J. E. Box, G. Feulner, M.E. Mann, A. Robinson, S. Rutherford, and E.J. Schaffernicht: Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation, Nature Clim. Change, 23 March 2015, 10.1038/nclimate2554.

[2] Hansen, J., M. Sato, P. Hearty, 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 Schuckemann, P. Kharecha, A.N. Legrande, M. Bauer, and K.-W. 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. Chem. Phys., 16, 3761-3812. doi:10.5194/acp-16-3761-2016.

[3] Saba, V.S., Griffies, S.M., Anderson, W.G., Winton, M., Alexander, M.A., Delworth, T.L., Hare, J.A., Harrison, M.J., Rosati, A., Vecchi, G.A., and Zhang, R.: Enhanced warming of the Northwest Atlantic Ocean under climate change, J. Geophys. Res., 120, doi:10.1002/2015JC011346, 2015.

[4] Ezeer, T. and L. P. Atkinson: Accelerated flooding along the U.S. East Coast: On the impact of sea-level rise, tides, storms, the Gulf Stream, and the North Atlantic Oscillations, Earth’s Future, 2, 362-382, 2014.

[5] Hall, T. and E. Yonekura: North American tropical cyclone landfall and SST: a statistical model study, J. Climate, 26, 8422- 8439, 2013.

July 2018 Global Temperature Update

July 2018 Global Temperature Update

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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.


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