By Ken Gregory, Friends of Science
Revised February 1, 2013 to include 2012 data.
The Economist magazine incorrectly claimed that Arctic warming was the result of greenhouse gas emissions from burning fossil fuels. Satellite data shows there has been no increase in the greenhouse effect in the Arctic region, so the warming could not have been caused by an increase in greenhouse gases. The Arctic is sheding more heat to space, uninhibited by greenhouse gases.
The Economist magazine article “The Melting North” June 16, 2012 states;
“There is no serious doubt about the basic cause of the warming. It is, in the Arctic as everywhere, the result of an increase in heat-trapping atmospheric gases, mainly carbon dioxide released when fossil fuels are burned. Because the atmosphere is shedding less solar heat, it is warming …”
http://www.economist.com/node/21556798
We can test this claim by measuring the increase in the greenhouse effect (GHE) in the Arctic region. The GHE is the difference between the surface temperature and the effective temperature at the top of the atmosphere. We use the National Oceanic and Atmospheric Administration (NOAA) satellite data to determine the heat escaping to space and the effective temperature of the Arctic region as viewed from space. (Definitions and data sources are shown below.)
The graph below shows the annual temperatures in the latitude band 60 degrees north to 85 degrees north as measured by satellites and ground stations from 1979 to 2012. The red curve is the GHCN/CAMS dataset, which is the actual average air temperature (not anomalies) 2 m above the ground. The satellite temperature data is the lower atmosphere temperature anomalies as determined by the University of Alabama in Huntsville (UAH). The surface temperature data is the combined land and sea surface temperatures anomalies (HadCRUT3) from the UK Climate Research Unit and the Hadley Centre of the UK Met Office. The satellite and surface temperature anomalies were adjusted to actual temperatures to match the GHCN/CAMS 1980 actual temperature.
The surface and satellite temperature trends from annual data, 1979 to 2012, are 0.40 C/decade and 0.47 Celsius/decade, respectively.
The apparent temperature of the earth when looking down from space is determined by measuring the outgoing longwave radiation (OLR) by satellites. The blue curve in the graph below shows the OLR from the NOAA database in the same northern latitude band as the temperature data, 60 N to 85 N. The corresponding emission temperature at the top of the atmosphere is shown by the red curve. The is the temperature that the top of the atmosphere must have to emit the heat radiation that was measured by the satellites.
The graph shows the OLR in the far north has increased significantly since 1993, contrary to the Economist article statement which incorrectly claimed “the atmosphere is shedding less solar heat”.
If there were no greenhouse gases, the atmosphere would be transparent to upward thermal radiation from the surface, so the temperature as seen from space would be the surface temperature, and the GHE would be zero. The greenhouse gases act as an insulating layer which causes the near-surface air temperature to be higher than the temperature at the top of the atmosphere. The GHE is just the difference between the surface temperatures and the effective TOA temperatures, as shown in the graph below.
The blue curve in the graph shows the change in the GHE from 1979 to 2012 from satellite lower atmosphere temperature data. The best fit line shows no trend. The red curve shows the change in the GHE based on surface temperature data. It shows an insignificant downward trend. Together, the two curves show that there has been no increase in the GHE in the far north.
This means that the increase in Arctic temperatures could not have been caused by anthropogenic greenhouse gas emissions. The warming may have been caused by black carbon from Asia, changes in ocean circulation, and less clouds due to an active Sun.
Ken Gregory
Friends of Science June 21, 2012
The effective TOA temperature T was determined by T = (OLR/sigma)0.25, where sigma = 5.6704 E-8 W/(m2K4).
NOAA OLR data is from http://climexp.knmi.nl/select.cgi?id=someone@somewhere&field=noaa_olr
HadCrut3 data is from http://climexp.knmi.nl/select.cgi?id=someone@somewhere&field=crutem3_hadsst2
UAH TLT data is from http://www.nsstc.uah.edu/public/msu/t2lt/uahncdc.lt New link http://vortex.nsstc.uah.edu/data/msu/t2lt/uahncdc_lt_5.6.txt
GHCN/CAMS data is from http://climexp.knmi.nl/select.cgi?id=someone@somewhere&field=ghcn_cams_25
Definition: Planetary Greenhouse Gas effect is the difference between effective emission temperature of a planet and global average temperature of its surface.
Definition: Effective Emission temperature is the temperature that a blackbody planet would need in order to emit the same amount of IR radiation as it could be measured from outer space by remote observer.
http://www.giss.nasa.gov/research/briefs/schmidt_05/
The size of the greenhouse effect is often estimated as being the difference between the actual global surface temperature and the temperature the planet would be without any atmospheric absorption, but with exactly the same planetary albedo, around 33°C.
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