By WUWT regular “Just The Facts”
Often in the climate debate, generalities are used to address more nuanced issues, e.g. “There is broad scientific consensus that Earth’s climate is warming rapidly and at an accelerating rate.” from the Wikipedia for Scientific Opinion on Climate Change. But is this true? Let’s take a look.
Global Surface Temperatures:
Generally, when referring to Earth’s “climate” warming, proponents of the Catastrophic Anthropogenic Global Warming (CAGW) narrative, refer to Earth’s Surface Temperature, e.g. “Global warming is the unusually rapid increase in Earth’s average surface temperature over the past century primarily due to the greenhouse gases released by people burning fossil fuels.” NASA Earth Observatory
As such, here’s NASA’s Goddard Institute for Space Studies (GISS) Monthly Mean Surface Temperature Anomaly – 1996 to Present;
NOAA’s National Climate Data Center (NCDC) Annual Global Mean Temperature Anomaly Over Land & Sea – 1880 to Present;
the UK Met Office’s – Hadley Center – Climate Research Unit (CRU) Annual Global Average Land Temperature Anomaly – 1850 to Present;
and the UK Met Office – Hadley Center – Climate Research Unit (CRU) Monthly Global Average Land Temperature – 1850 to Present
Depending on the time frame, it certainly seems that Earth’s surface temperature has increased, though it does not appear to be “warming rapidly” and there are no indications of “an accelerating rate”. Furthermore, the surface temperature record is burdened with issues of questionable siting, changes in siting, changes in equipment, changes in the number of measurement locations, modeling to fill in gaps in measurement locations, corrections to account for missing, erroneous or biased measurements, and the urban heat island effect. Thus to see the big picture on the temperature Earth’s temperature, it helps to also look up.
Since 1979 the temperature of Earth’s “climate” has also been measured via satellite. “The temperature measurements from space are verified by two direct and independent methods. The first involves actual in-situ measurements of the lower atmosphere made by balloon-borne observations around the world. The second uses intercalibration and comparison among identical experiments on different orbiting platforms. The result is that the satellite temperature measurements are accurate to within three one-hundredths of a degree Centigrade (0.03 C) when compared to ground-launched balloons taking measurements of the same region of the atmosphere at the same time.” NASA
RSS Temperature Lower Troposphere (TLT) – Brightness Temperature Anomaly- 1979 to Present;
RSS Temperature Middle Troposphere (TMT)- Brightness Temperature Anomaly- 1979 to Present;
RSS Temperature Troposphere / Stratosphere (TTS) -Brightness Temperature Anomaly- 1987 to Present;
RSS Temperature Lower Stratosphere (TLS) – Brightness Temperature Anomaly – 1979 to Present:
According to Remote Sensing Systems, “For Channel (TLT) (Lower Troposphere) and Channel (TMT) (Middle Troposphere), the anomaly time series is dominated by ENSO events and slow tropospheric warming. The three primary El Niños during the past 20 years are clearly evident as peaks in the time series occurring during 1982-83, 1987-88, and 1997-98, with the most recent one being the largest.” RSS
Also, the 2009 – 10 El Niño event is also called out on this RSS Latitudinal Temperature Lower Troposphere (TLT) Brightness Temperature Anomaly from 1979 to Present;
and the 1998 El Niño event, along with the tropospheric cooling attributed to the 1991 eruption of Mt Pinitubo, is called out on this University of Alabama – Hunstville (UAH) Lower Atmosphere Temperature Anomalies – 1979 to Present:
Note that in November the UAH Lower Atmosphere Temperature Anomaly was 0.12 degrees C above the 30 year average, and the RSS Lower Troposphere Brightness Temperature was 0.033 degrees C above the 30 year average. Keep this mind the next time you read that recent weather events were caused by Global Warming.
Furthermore, the Middle Troposphere, which follows a similar though flatter trend as the Lower Troposphere, recently dipped below the 30 year trend line i.e. RSS Temperature Middle Troposphere (TMT)- Brightness Temperature Anomaly- 1979 to Present:
There are also regional variations in Lower Troposphere that contribute nuance to the picture. For example, RSS Northern Polar Temperature Lower Troposphere (TLT) Brightness Temperature Anomaly;
shows a .338 K/C per decade increase, whereas the The RSS Southern Polar Temperature Lower Troposphere (TLT) Brightness Temperature Anomaly;
shows a .007 K/C per decade decrease. I am not aware of a compelling explanation for the significant divergence in temperature trends between the poles.
The satellite record seems to show slow warming of Lower and Middle Tropospheric temperatures, overlaid with the El Niño/La Niña Southern Oscillation (ENSO) cycle, including four comparatively large El Niño events. Lower Tropospheric temperatures appear to have flattened since the large El Niño in 1998 and offer no indication of “accelerating” warming.
Moving higher in the atmosphere, RSS Temperature Troposphere / Stratosphere (TTS) – Brightness Temperature Anomaly- 1987 to Present;
has been incredibly flat since, with a trend of just -.004 K/C per decade. The 1997-98 and 2009 – 10 El Niño events are still readily apparent in the plot, as is a spike from the 1991 eruption of Mt. Pinatubo. Note that the effect of Mt. Pinatubo is the opposite in the Lower and Middle Troposphere versus the Troposphere / Stratosphere (TTS), i.e. “Large volcanic eruptions inject sulfur gases into the stratosphere; the gases convert into submicron particles (aerosol) with an e-folding time scale of about 1 year. The climate response to large eruptions (in historical times) lasts for several (2-3) years. The aerosol cloud causes cooling at the Earth’s surface, warming in stratosphere.”
It is interesting that, incorporating the impact of three significant surface driven warming events, Troposphere / Stratosphere Temperatures (TTS) have been quite stable, however there is nuance to this as well.
RSS Northern Hemisphere Temperature Troposphere / Stratosphere (TTS) – Brightness Temperature Anomaly- 1987 to Present;
has been increasing by .054 K/C per decade, whereas the RSS Southern Hemisphere Temperature Troposphere / Stratosphere (TTS) – Brightness Temperature Anomaly- 1987 to Present;
has been decreasing by -.062 K/C per decade.
Moving higher still in the atmosphere, the RSS Temperature Lower Stratosphere (TLS) – Brightness Temperature Anomaly – 1979 to Present;
“is dominated by stratospheric cooling, punctuated by dramatic warming events caused by the eruptions of El Chichon (1982) and Mt Pinatubo (1991).” RSS
The eruptions of El Chichon and Mt Pinatubo are readily apparent in the Apparent Atmospheric Transmission of Solar Radiation at Mauna Loa, Hawaii:
“The stratosphere” … “in contrast to the troposphere, is heated, as the result of near infrared absorption of solar energy at the top of the aerosol cloud, and increased infra-red absorption of long-wave radiation from the Earth’s surface.”
“The stratospheric warming in the region of the stratospheric cloud increases the latitudinal temperature gradient after an eruption at low latitudes, disturbing the stratospheric-troposphere circulation, increasing the difference in height of the troposphere between high and low latitudes, and increasing the strength of the jet stream (polar vortex, especially in the northern hemisphere). This leads to warming during the northern hemisphere winter following a tropical eruption, and this warming effect tends to be larger than the cooling effect described above.” Ellen Thomas, PHD Wesleyan University
The Lower Stratosphere experienced “dramatic warming events caused by the eruptions of El Chichon (1982) and Mt Pinatubo (1991).” RSS “The long-term, global-mean cooling of the lower stratosphere stems from two downward steps in temperature, both of which are coincident with the cessation of transient warming after the volcanic eruptions of El Chichon and Mt. Pinatubo.” … “Here we provide observational analyses that yield new insight into three key aspects of recent stratospheric climate change. First, we provide evidence that the unusual step-like behavior of global-mean stratospheric temperatures is dependent not only upon the trend but also on the temporal variability in global-mean ozone immediately following volcanic eruptions. Second, we argue that the warming/cooling pattern in global-mean temperatures following major volcanic eruptions is consistent with the competing radiative and chemical effects of volcanic eruptions on stratospheric temperature and ozone. Third, we reveal the contrasting latitudinal structures of recent stratospheric temperature and ozone trends are consistent with large-scale increases in the stratospheric overturning Brewer-Dobson circulation” David W. J. Thompson Colorado State University
Above the Stratosphere we have the Mesosphere and Thermosphere, neither of which have I found current temperature time series for, but of note is that on “July 15, 2010” “A Puzzling Collapse of Earth’s Upper Atmosphere” occurred when “high above Earth’s surface where the atmosphere meets space, a rarefied layer of gas called “the thermosphere” recently collapsed and now is rebounding again.”
“This is the biggest contraction of the thermosphere in at least 43 years,” says John Emmert of the Naval Research Lab, lead author of a paper announcing the finding in the June 19th issue of the Geophysical Research Letters (GRL). “It’s a Space Age record.”
The collapse happened during the deep solar minimum of 2008-2009—a fact which comes as little surprise to researchers. The thermosphere always cools and contracts when solar activity is low. In this case, however, the magnitude of the collapse was two to three times greater than low solar activity could explain.
“Something is going on that we do not understand,” says Emmert.
The thermosphere ranges in altitude from 90 km to 600+ km. It is a realm of meteors, auroras and satellites, which skim through the thermosphere as they circle Earth. It is also where solar radiation makes first contact with our planet. The thermosphere intercepts extreme ultraviolet (EUV) photons from the sun before they can reach the ground. When solar activity is high, solar EUV warms the thermosphere, causing it to puff up like a marshmallow held over a camp fire. (This heating can raise temperatures as high as 1400 K—hence the name thermosphere.) When solar activity is low, the opposite happens.” NASA
In summary, Earth’s Lower and Middle Troposphere appear to have warmed slowly, overlaid with the El Niño/La Niña Southern Oscillation (ENSO) cycle, including four comparatively large El Niño events, and tempered by the cooling effects of the eruption of El Chichon (1982) and Mt Pinatubo (1991). Lower and Middle Tropospheric temperatures appear to have flattened since the large El Niño in 1998 and offer no indication of “accelerating” warming. Tropospheric / Stratospheric temperatures appear to have been influenced by at least three significant surface driven warming events, the 1997-98 El Niño, and the eruptions of El Chichon in 1982 and Mt Pinatubo in 1991, but to have maintained a stable overall trajectory. Stratospheric temperatures appear to have experienced two “dramatic warming events caused by the eruptions of El Chichon (1982) and Mt Pinatubo (1991).”, and “unusual step-like behavior of global-mean stratospheric temperatures” which has resulted in a significant stratospheric cooling during the last 30 years. Lastly, “during deep solar minimum of 2008-2009” “the biggest contraction of the thermosphere in at least 43 years” occurred and “The magnitude of the collapse was two to three times greater than low solar activity could explain.”
“The oceans can hold much more heat than the atmosphere. Just the top 3.2 metres of ocean holds as much heat as all the world’s air.” Commonwealth of Australia – Parliamentary Library
As such, changes in Oceanic Oscillations, and Ocean Heat Content are critical to understanding “Earth’s Temperature”. Here is NOAA’s NODC Global Ocean Heat Content from 0-700 Meters – 1955 to Present;
and here is the same from Ole Humlum’s valuable climate data site Climate4you.com, NODC Global Ocean Heat Content – 0-700 Meters – 1979 to Present.
It seems apparent from the plots above that Global Ocean Heat has increased over the last several decades, however Global Ocean Heat doesn’t appear to be “warming rapidly”. Furthermore, there is no basis for the claim that warming is occurring at “an accelerating rate”. Decelerating would appear a more accurate label.
A proxy often cited when measuring “Earth’s Temperature” is amount of Ice on Earth. According to the United States Geographical Survey (USGS), “The vast majority, almost 90 percent, of Earth’s ice mass is in Antarctica, while the Greenland ice cap contains 10 percent of the total global ice mass.” http://ga.water.usgs.gov/edu/watercycleice.html However, there is currently there is no generally accepted measure of ice volume, as Cryosat is still in validation and the accuracy of measurements from Grace are still being challenged.
As such, currently available global ice measurements are limited. Here is 20 Year Northern Hemisphere Snowcover with 1995 – 2009 Climatology
and here is Northern Hemisphere Winter Snow Extent – 1967 to Present:
While neither plot offers a global perspective, when looking at the Northern Hemisphere, there appears to have been a slight increase in Snowcover and Winter Snow Extent over the historical record.
Another ice based variable often cited as a proxy for “Earth’s Temperature” is Sea Ice Area, however there is significant evidence that the primary agent of change in Sea Ice Area is in fact wind and Atmospheric Oscillations. With this said, here are Global, Arctic & Antarctic Sea Ice Area from 1979 to Present;
Northern Hemisphere Sea Ice Area Anomaly, 1979 to Present;
Southern Hemisphere Sea Ice Area Anomaly, 1979 to Present;
and Global Sea Ice Area Anomaly – 1979 to Present:
There does appear to have been a negative trend in Northern Hemisphere Sea Ice Area, however there also appears to have been a positive trend in Southern Hemisphere Sea Ice Area. The resultant Global Sea Ice Area trend appears to be slightly negative, with no apparent acceleration. Based on the limited Global Ice measurements available, and noting the questionable value of Sea Ice Area as a proxy for temperature, not much inference can currently be drawn from Earth’s Ice measurements. However, there does not appear to be any evidence in Earth’s Ice measurements of rapid and/or accelerating warming.
“Earth’s Temperature” appears to have increased during the last several decades, but there does not appear to be evidence that Earth’s climate is “warming rapidly”. Furthermore, there are no apparent signs of warming occurring “at an accelerating rate”.