Guest essay by Bob Irvine
Is it true that energy from either an outside source or an increase in insulation will warm a system according to or in proportion to its residence time in that system?
If true, this might explain why changes in GHG concentrations appear to have less affect on global temperatures than similar changes in solar forcing.
1. It is not contested that a black box that absorbs solar energy more efficiently will be warmer inside than a white box with a reflective surface. Is the reason for this that the solar energy has a much shorter residence time in the reflective white box than it does in the black box?
2. If we imagine a change in solar activity that adds 1 W/M2 of energy to the earth system. Some of this energy is deposited directly into the atmosphere and land surface where it is returned relatively quickly to space. A large portion of this energy is, however, deposited directly and by radiation into the oceans. This energy can remain circulating in the oceans for many years sometimes up to 1000s of years. It has an extremely long residence time.
3. Now, can we imagine a similar change in GHG concentration that adds similarly 1 W/M2 to the earth system. These extra GHGs largely and initially affect the atmosphere as they add to the earth’s radiative emission height to space. The water vapour feedback mechanism also works largely in this way. This higher average emission height warms the earth system initially high in the tropical troposphere and by convection the whole atmosphere is warmed. This energy is returned to space relatively quickly.
This warmer atmosphere then insulates the oceans and the oceans become warmer as a result. The energy that is trapped this way in the ocean has an extremely long residence time in the earth system. GHGs do not warm the oceans significantly by radiation.
4. The mechanisms by which a change in GHG concentration and a change in solar activity affect the earth’s surface temperature and heat content are very different with the residence time of the GHG energy likely to be significantly shorter than the residence time of the extra solar energy. If this is true, then the efficacy of a GHG forcing would be significantly lower than the efficacy of a similar solar forcing.
5. Nearly all sensitivity studies base their feedbacks on the assumption that GHG and solar efficacy are approximately equal. The IPCC states this in their reports. The feedbacks used are then feedbacks to an initial warming while feedbacks related to the intrinsic nature of the forcing and its mechanism are not normally considered. In particular, changes in residence times for energy from the different forcings do not appear to be considered.
6. If we give solar activity changes 4 times the efficacy of GHG changes then the Energy Balance Model below can be produced. It is not a bad match with the actual measured temperature and indicates that sensitivity studies should not assume that these efficacies are similar.
7. The model below uses Aerosols, Solar and GHG forcing only and has a reasonable internal variability included based on the PDO and AMO indexes. The change in equilibrium temperature for 1 W/M2 of solar change was 1.4C while a similar change in GHG forcing was assumed to produce about 0.35C of warming at equilibrium or about 1.3C for CO2 doubling. Aerosol forcing is at the lower end of the IPCC range. The differences from 1980 to 2000 may be due to volcanic activity not being included.
8. The higher solar sensitivity fits well with millennial temperature and solar forcing estimates. The variation in millennial temperatures can only be explained by higher solar sensitivity.
9. This Energy Balance Model certainly is a curve fitting exercise, but it does produce the cooling period from 1940 to 1970 and the current temperature hiatus and should be taken into consideration for these reasons.
“This implies that GHG energy is returned to the atmosphere and space very quickly as latent heat of evaporation while solar energy is effectively absorbed to a depth of many meters with consequent delays in equilibrium at the Top of the Atmosphere (TOA).”
It’s apparently too obvious.
“I know that most men, including those at ease with problems of the greatest complexity, can seldom accept even the simplest and most obvious truth if it be such as would oblige them to admit the falsity of conclusions which they have delighted in explaining to colleagues, which they have proudly taught to others, and which they have woven, thread by thread, into the fabric of their lives.”
― Leo Tolstoy