In a comment placed on the my previous post, one reader pointed out that “all sides” of the global warming issue should be heard and carefully considered. I agree entirely but only as long as the consensus view of Science is being included as one of those “sides”. Furthermore, when someone claims that the “theory” of AGW is just a Hoax without a scientific basis, I expect them to be aware, at least, of the essence of what that theory is. Therefore, it might be helpful at this point to remind all of us what, in a concise and an easily digestible form, does Science say about this issue. It centers on what is called the “greenhouse effect” and goes like this:
The effect of adding man-made CO2 is predicted in the THEORY of greenhouse gases. If a scientific theory is shown to be a good one, it will have ‘predictive power’ and those predictions are likely to come true. So first, what is the greenhouse effect?
The greenhouse gas theory was first proposed by Swedish scientist Svante Arrhenius in 1896, based on earlier work by Fourier and Tyndall. Many scientists have refined the theory in the last century. Nearly all of these have reached the same conclusion: if we increase the amount of greenhouse gases in the atmosphere, the Earth will warm up.
The predicted AMOUNT of greenhouse warming is still a work in progress. This issue is called ‘climate sensitivity’, defined to be the amount the average temperature will increase if CO2 is doubled from pre-industrial levels. Climate models have predicted the least temperature rise would be on average 1.65°C (2.97°F) , but upper estimates vary a lot, averaging 5.2°C (9.36°F). Current best estimates are for a rise of around 3°C (5.4°F) for a doubling of CO2.
The greenhouse effect works like this: Energy arrives from the sun in the form of visible light and ultraviolet radiation. The Earth then attempts to cool itself by its emission of longer wavelength infrared radiation into outer space. The greenhouse gases in the atmosphere will ‘capture’ some of that infrared radiation, however, and then re-emit it in all directions – including back to the Earth’s surface – thus warming it.
We are fortunate that we have a strong greenhouse effect. CO2 and other greenhouse gases keep the Earth’s surface about 33°Celsius (59.4°F) warmer than it would be without them. But we have now added 42% more CO2 to the atmosphere during the Industrial Age, and temperatures have increased further – by about 0.8 degrees C (1.4°F). We are presently adding about 0.6% more CO2 to the atmosphere every year mainly via the combustion of fossil fuels.
In addition to temperature measurements, we can also measure the infrared radiation referred to above. This is easily done with instruments placed on the surface of the Earth and for several decades now we have also been able to make such measurements via satellites of the infrared radiation that is leaving the Earth. During recent decades – when CO2 levels and temperatures have increased the most – the observed emissions of upward infrared radiation have continuously decreased and those of downward infrared radiation have continuously increased exactly at the wavelengths associated with the greenhouse gases. These measurements also tell us that the Earth is warming and, furthermore, they tell us why.
In summary, as temperatures started to rise in recent decades, scientists became more and more interested in the cause. Many theories were proposed. All save one have fallen by the wayside and have been discarded for a lack of evidence. One theory alone has stood the test of time, increasingly strengthened by experiments.
Unfortunately, not liking the predictions of a given theory is not sufficient grounds for discarding or even doubting it. That is, Mother Nature seems to do her own thing without notice of the preferences of human beings. At the same time, Science has historically provided our best estimates of what Mother Nature is likely to do. Therefore, when posting comments here concerning the science of climate, I would encourage the commenter to keep this “opinion” of modern Science in mind and consider how their own “new insights” might possibly affect that consensus view. At the very least, I think the fields of science deserve this level of respect and more importantly, starting discussions with “what science thinks” spares us the need to “reinvent the wheel” in every discussion of this issue. Saying simply that “Svante Arrhenius was a fool” will not cut it here.
ericgrimsrud 
Eric said: “During recent decades – when CO2 levels and temperatures have increased the most – the observed emissions of upward infrared radiation have continuously decreased and those of downward infrared radiation have continuously increased exactly at the wavelengths associated with the greenhouse gases.”
Eric: You will notice that since around 2003 the annual series smoothed with a 21-point binomial filter shows a distinct drop in temperature and I guess they were not able to hide this decline.
HadCRUT3 Diagnostics: global average (NH+SH)/2 http://www.metoffice.gov.uk/hadobs/hadcrut3/diagnostics/global/nh%2Bsh/index.html
HadCRUT.4.2.0.0 (current version)
This is the current version of HadCRUT4. Previous versions of the dataset are available here.
You will notice when you open this link below that atmospheric CO2 has been steadily increasing since 1960 and, if this is true and you maintain that it is the driver of the earth’s temperature, then why have these temperature now dropped and why was the Medieval Warm Period warmer than the temperature of to day?
Full Mauna Loa CO2 record
http://www.esrl.noaa.gov/gmd/ccgg/trends/
One can only wonder at why in your “Just an Opinion – What Science Thinks” did not make any mention of H2O in its various forms in the atmosphere and the fact that it is accountable for 95-8% of the green house effect and constitutes .4 of the atmosphere while CO2 comes in at.038-9% All of the water in the earth’s rivers, lakes, snow banks, whatever, at one time was in the atmosphere as part of the ongoing water cycle but you seem to want to totally discount it from the equation.
You can look at this link and imagine at what clouds might have to do with the climate and the assertion that 95-8% of the green house effect is due to H2O in various forms in the atmosphere.
http://www.nytimes.com/interactive/2012/05/01/science/earth/0501-clouds.html
I can imagine that you have never wondered at why the coldest nights of the winter happen when there is no cloud cover or why it can get to extremely hot temperatures in the deserts during the day time and freeze at night; again, no cloud cover to hold the heat or to shade the desert area in the day time.
Eric: How is it that Rajendra Pachauri can admit this below but you seem to not want to do so?
THE UN’s climate change chief, Rajendra Pachauri, has acknowledged a 17-year pause in global temperature rises, confirmed recently by Britain’s Met Office, but said it would need to last “30 to 40 years at least” to break the long-term global warming trend.
Dr Pachauri, the chairman of the UN’s Intergovernmental Panel on Climate Change, said that open discussion about controversial science and politically incorrect views was an essential part of tackling climate change.
Phil Jones, downplayed the significance of the latest findings but did not deny them, outright.
“We don’t fully understand how to input things like changes in the oceans, and because we don’t fully understand it you could say that natural variability is now working to suppress the warming,” Jones admitted to the paper, apparently acknowledging what skeptical climate scientists have been attempting to convey for years. “We don’t know what natural variability is doing.”
[RESPONSE FROM EPG: John, Your argument that the Earth is not warming hinges of one factor – that is the large thermal inertia of the Earth and the fact that about 95% of the extra heat caused by our increasing GH effect gets hidden a bit in the depth of the oceans. Still it is clear that even surface temperatures in the last several decades have increased. In the 20th and 21st centuries no decade has been cooler than the previous one. The decadal average temperatures only go up. In addition, the amount of ice over the Arctic Ocean is now a fraction of what is was 100 years ago. Your claim that the heat content of the Earth is not increasing is really quite silly.
And of course, water vapor is the main greenhouse gas in the atmosphere (at low elevations only). But for the 100th time, what determines the amount of water vapor in the lower atmosphere? The answer is temperature. Increased T causes increase water vapor. Thus the effect of the permanent GHGs including CO2 is amplified by its effect on water vapor. So we now do appear to have increased H2O in the lower atmosphere – and this is another indication of greater global temperatures. It also explains why we are having increased floods and severe weather events. Floods, of course, come from increase water vapor and the energy driving storms comes from the condensation of water vapor when a humid air mass hits a cooler one. More water vapor, more power in the storms.
Again, John, the factor that has you confused is simply the large thermal inertial of the Earth and its oceans, in particular. There is not doubt that the total heat content of the Earth is increasing. Furthermore the infrared radiation measurements I summarized in my post dictate that this must be so – whenever the electromagnetic emissions of an object decrease, the heat content of that object has to be increasing – assuming the heat input (from the Sun in this case) is remaining relatively constant. So if you are claiming no increase in the heat content of the Earth, you must be claiming that the heat input from the Sun is decreasing – and there is no evidence for that as far as I know. }
By: John D. Swallow on August 12, 2013
at 4:57 am