Here is a great chart that very nicely shows the key heat flows that determine the earth's surface temperature:
Credits: From Kiehl, J. T. and Trenberth, K. E. (1997). "Earth's Annual Global Mean Energy Budget". Bulletin of the American Meteorological Association 78: 197-208.
The chart above and the text and chart just below are from windows2universe article.
For the past several thousand years, up until the last couple of centuries, average CO2 concentration hovered in the 250 to 280 ppmv range. Ice core data indicates that CO2 concentration hadn't previously risen above 300 ppmv in at least the past 300,000 years. Less direct geologic records appear to indicate that the last time CO2 concentration was as high as it is today was about 20 million years ago. The graph below, which includes both direct measurements and ice core data, shows that carbon dioxide levels have been steadily rising since at least about 1850; and have risen sharply since around 1950. This rise corresponds to a period of dramatically increased CO2 emissions from the burning of fossil fuels that have been used to power humanity's industrial revolution. Atmospheric CO2 concentration has risen at least 35% above pre-industrial levels (from 280 to 380 ppmv).
For the past several thousand years, up until the last couple of centuries, average CO2 concentration hovered in the 250 to 280 ppmv range. Ice core data indicates that CO2 concentration hadn't previously risen above 300 ppmv in at least the past 300,000 years. Less direct geologic records appear to indicate that the last time CO2 concentration was as high as it is today was about 20 million years ago. The graph below, which includes both direct measurements and ice core data, shows that carbon dioxide levels have been steadily rising since at least about 1850; and have risen sharply since around 1950. This rise corresponds to a period of dramatically increased CO2 emissions from the burning of fossil fuels that have been used to power humanity's industrial revolution. Atmospheric CO2 concentration has risen at least 35% above pre-industrial levels (from 280 to 380 ppmv).
 Credit: Robert A. Rohde and the Global Warming Art project. |
There are other atmospheric components besides CO2 impacting temperatures at the earth's surface (manmade and volcanic sourced sulfates in the air, ash and aerosols from volcano activity, ozone, methane, variations in solar levels). The below plot shows the trends and effects of several of these. For the detailed explanations of the data in this plot refer to its source: Climate Change Attribution. The full model that considers CO2 plus other factors actually comes quite close to matching the observed temperature trends of the past 100 years.
This figure, based on Meehl et al. (2004), shows the ability with which a global climate model (the DOE PCM [1]) is able to reconstruct thehistorical temperature record and the degree to which the associated temperature changes can be decomposed into various forcing factors. The top part of the figure compares a five year average of global temperature measurements (Jones and Moberg 2001) to the Meehl et al. results incorporating the effects of five predetermined forcing factors: greenhouse gases, man-made sulfate emissions, solar variability, ozone changes (both stratospheric and tropospheric), and volcanic emissions (including natural sulfates). The time history and radiative forcing qualities for each of these factors was specified in advance and was not adjusted to specifically match the temperature record.
The data are complex, but they clearly indicate that mankind's activities have caused world average temperatures to rise over the past 100 years, and, according to the modeling, the single biggest factor driving this change is the rise in atmospheric CO2 level.
What makes the situation of more concern is that there are secondary effects that are already starting to kick in. Warming that has already occurred is leading to the melting and retreat of glaciers and ice packs. With less ice cover, direct reflectance of sunlight energy is reduced and so there is more warming. Warming that has already occurred is also leading the thawing of permafrost and this is causing the release of more greenhouse gases.
It could be that all of the warming will just cause the oceans to rise and nothing else bad will come of it. But with numerous secondary and interactive effects its not at all certain how fast the warming will come, where the warming will stop, and how high the oceans will have risen by the time it does stop. Given that the impact of a 3 or 4 deg F rise in global temperature could well be disastrous, I think it makes a lot of sense to at least think about backing off some on our activities that are contributing to the warming.
A couple more very good charts:
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| Global mean land-ocean temperature change from 1880–2011, relative to the 1951–1980 mean. The black line is the annual mean and the red line is the 5-year running mean. The green bars show uncertainty estimates. Source: NASA GISS. |
How global surface temperature, ocean heat and
atmospheric CO2 levels have risen since 1960
THE record of
atmospheric carbon-dioxide levels started by the late Dave Keeling of the
Scripps Institute of Oceanography is one of the most crucial of the data sets
dealing with global warming. When the measurements started in 1959 the annual
average level was 315 parts per million, and it has gone up every year since.
To begin with it went up by roughly one part per million per year. Now it is
more like two parts per million per year. The figure for 2011 is 391.6. More
carbon dioxide in the atmosphere means a stronger greenhouse effect, and
various measurements speak to this. Global surface temperature records show a
warming over the same period, though because of fluctuations in the climate,
air pollution, volcanic eruptions and other confounding factors the rise is
nothing like as smooth. A steadier rise can be seen in the heat content of the
oceans, measured in terms of the energy stored, rather than the temperature.
May 2nd 2012, 14:00 by The Economist Online
How global surface temperature, ocean heat and atmospheric CO2 levels have risen since 1960
THE record of atmospheric carbon-dioxide levels started by the late Dave Keeling of the Scripps Institute of Oceanography is one of the most crucial of the data sets dealing with global warming. When the measurements started in 1959 the annual average level was 315 parts per million, and it has gone up every year since. To begin with it went up by roughly one part per million per year. Now it is more like two parts per million per year. The figure for 2011 is 391.6. More carbon dioxide in the atmosphere means a stronger greenhouse effect, and various measurements speak to this. Global surface temperature records show a warming over the same period, though because of fluctuations in the climate, air pollution, volcanic eruptions and other confounding factors the rise is nothing like as smooth. A steadier rise can be seen in the heat content of the oceans, measured in terms of the energy stored, rather than the temperature.
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One of the best comprehensive articles on global warming can be found here: http://en.wikipedia.org/wiki/Global_warming
One of the best comprehensive articles on global warming can be found here: http://en.wikipedia.org/wiki/Global_warming
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