Does one have to deny that the so-called green house gases (GHG)s have an effect on global temperatures to be a skeptic? Many of the big-league skeptics believe that the GHGs do play a part in global temperature. So maybe not.
The following is a quote from Climate Change Reconsidered II** :
“ As carbon dioxide concentrations increase so too does the intensity of back radiation at the surface across the active wavebands of CO2, and because this radiation emanates from a lower and warmer layer of the atmosphere, the magnitude of the back radiation increases. Consequently, the net infrared radiation emanating from the surface is reduced, causing a rise in temperature that generates increased heat exchange and evaporation. This surface warming also contributes to an increase in convective instability”.
So, hold on and let me explain why I believe this.
First, a look at the big picture. The Sun’s surface is somewhere about 5500 C. Radiation goes out in all directions with some of it directed toward Earth. This is Earth’s principal source of energy. This radiation travels 93 million miles in about 8 minutes to reach Earth. It loses much of its strength in the journey, but at the top of our atmosphere, its strength is nominally 1365 watts per square meter. The Sun’s radiation mainly consists of photons of visible light, ultraviolet and infrared. The full force of the Sun’s radiation seldom reaches the Earth surface because of clouds, reflection off snow and ice, scattering in the atmosphere for example and the angle that the Sun’s rays strike the surface. Further complicating this topic is the fact on average, the Sun only shines on any place on Earth for more than 12 hours per day.
Many charts showing the Earth’s average energy budget use 340 w/m² because when you factor in the length of the day and the spherical geometry of the Earth the effect is about ¼ the energy at the top of the atmosphere at noon. While the Energy budget charts are useful, I believe they get in the way of understanding the GHG effect. So, the following will uses actual measured radiation data and not the hypothetical 340w/m².
To get an idea of what happens at the surface, lets take a look at the data collected by the Surface Radiation Project. The Surface Radiation Budget Network (SURFRAD) was established in 1993 through the support of NOAA’s Office of Global Programs. The SURFRAD mission is clear:
“its primary objective is to support climate research with accurate, continuous, long-term measurements of the surface radiation budget over the United States”.
SURFRAD currently has 7 operating stations. These stations are very well equipped. They can measure upwelling and downwelling solar, upwelling and downwelling IR, temperature, RH, wind speed, cloud cover, UVb and several others. The SURFRAD website allows you to make charts of the collected day. For starters I have plotted some data from the Desert Rock, Nevada SURFRAD site.
On the top chart, I plotted downwelling and upwelling solar and downwelling and upwelling IR for this 24-hour plot of the station at Desert Rock, Nevada on the 30th of June this year.
The red line shows the sun rising about 5am local standard time (LST) and it had set on the previous day at 7 pm. The w/m² are at a maximum about noon when the Sun is directly over the Earth’s surface. The blue line is the upwelling solar, probably reflected, that did not cause any rise in the surface radiation. This was a very sunny day at Desert Rock. And this is confirmed by the bottom chart showing a maximum temperature that day of 39C (102F)
The Sun’s radiant energy heats the Earth’s surface. The surface begins to emit infrared(IR) radiation (upwelling). The radiation is a function of the temperature of the surface just as the Suns radiation was a function of the Sun’s surface temperature. The difference in temperature between the Sun and the Earth’s surface is vast. The energy from the Sun is composed of radiation with extremely short wave lengths. The wave lengths produced by the Earth’s radiation are much longer and are called longwave.. This is an important insight because it allows the researchers to distinguish between Sun and Earth sourced radiation.
The upwelling Earth’s IR is illustrated by the brown line. The green line is the measured downwelling of IR from the atmosphere.
As the solar radiation reaches the surface, the temperature begins to rise causing the upwelling IR to rise and one can note there is a small rise in downwelling IR, The up and downwelling radiation are measured on very sophisticated devices. The atmosphere is heating as well and the GHGs are emitting IR back to the surface.
There is no solar radiation at night, and yet there is up and down welling radiation during that time? Obviously the surface and the gases in the atmosphere are radiating.
This by itself should demonstrate that what we are measuring is from the surface and the atmosphere, not solar radiation – otherwise the night-time radiation would drop to zero.
So what is going on? The big picture is: Energy from the Sun is striking the surface. Energy is being returned into space from the Earth. Research satellites are orbiting the Earth measuring the outflow of energy and they show that the Sun’s energy input is matched by the energy output. The warmers say that there is an imbalance of about 1W/m² and that 1W/m² is heating the Earth. I kind of doubt that the measurement confirms that conclusion. I think it is probably back calculated based upon how big the imbalance would be required to heat the globe to their estimate of warming.
Ok, but what does that have to do with downwelling IR and GHGs.
The Sun’s radiation is little packets of energy as photons. The Sun’s radiation does very little heating of the atmosphere, it basically heats the surface. As the day progresses, the Sun keeps putting this energy into the surface faster than the atmosphere can release it into space. The surface gets hotter and as it does it emits more IR. The GHGs are absorbing surface IR photons thus impeding the surface IR trip back into space. Furthermore, the GHGs are reemitting photons back down to the surface. If there were no GHG effect the surface radiation would go directly out to space and there would be no downwelling IR radiation.
Some additional explanation is required here. The GHGs reemissions of IR photons are actually done in all directions, not just downward. Some emissions are going up in the atmosphere where they can be absorbed by other GHGs in the atmosphere until such time finally are able to reach space. Also at the same time, the energized GHG molecules are bumping to other molecules (N2 and O2, mostly) in the atmosphere and transferring heat to them by conduction. Water vapor absorbs and reemits IR photons and it also functions as a means of convection cooling. Water vapor is evaporated and climbs upward where it cools and condenses and releases energy. Most studies I have read credit water vapor as the primary vehicle for returning heat to space.
As the surface temperature rises, it eventually reaches a point where the upwelling radiation balances the incoming solar radiation. This satisfies the overall daily energy balance. As the solar radiation recedes, the upwelling radiations begins to recede and and continues to do so overnight.
Some people do not think that the downwelling IR exists. To quote Dr. Roy Spencer about what the measured data show:
“There are upward-viewing radiometers making measurements at hundreds of wavelengths, clearly showing CO2 emission and water vapor emission at the wavelengths more sensitive to these gases. There is no other possible explanation for these things.
For another way to look at the GHG effect, go to Does the Greenhouse Gas Effect really exist—Part 2
I was planning on publishing Part 1 and Part 2 on Sunday and Monday (26 and 27 November) but this morning read the new Willis Echenbach posting on WUWT that explains how the downwelling long wave IR heats the surface. I recommend that you read it.
** These are the authors of Climate Change Reconsidered II:
Lead Authors/Editors Craig D. Idso (USA), Robert M. Carter (Australia), S. Fred Singer (USA)
Chapter Lead Authors Timothy Ball (Canada), Robert M. Carter (Australia), Don Easterbrook (USA), Craig D. Idso (USA), Sherwood Idso (USA), Madhav Khandekar (Canada), William Kininmonth (Australia), Willem de Lange (New Zealand), Sebastian Lüning (Germany), Anthony Lupo (USA), Cliff Ollier (Australia), Willie Soon (USA)
Contributing Authors J. Scott Armstrong (USA), Joseph D’Aleo (USA), Don Easterbrook (USA), Kesten Green (Australia), Ross McKitrick (Canada), Cliff Ollier (Australia), Tom Segalstad (Norway), S. Fred Singer (USA), Roy Spencer (USA)
This group of skeptics call themselves the NonIntergovernmental Panel on Climate Change (NIPCC) which is to separate their work from that of the UN’s IPCC—-a group of certified warmers.