Douglas Hoyt (bio and references)

Email: dhoyt@toast.net

On these web pages we take a critical look at climate change and particularly climate change over the last 25 years where data is good. Some of the material comes from an old website at erols.com that now no longer exists. Much of material will be new based on new developments in the last few years.

The material is organized into several categories, with introductory statements on this page and more detail discussion in the links. The material will be updated form time to time.


There are several problems with the theoretical underpinnings of the standard IPCC theory of global warming due to anthropogenic greenhouse gases (AGHG). These problems are listed here with more discussion in the links.

1. The IPCC theory has a roughly 3.5 W/m2 decrease in outgoing thermal radiation from a doubling of carbon dioxide. The number is based upon an instantaneous doubling of carbon dioxide and assumes no change in the continuum radiation. This topic is discussed further here.

2. The sensitivity of climate without any feedbacks is (33 C / 148 W/m2) or 0.22 C/W/m2, so the basic change in climate is 0.22 * 3.5 C or 0.7 C for a doubling of carbon dioxide. Recently Schwartz has deduced empirically that the climate sensitivity is approximately 0.25 C/W/m2, and equilibrium time is 2-3 years (Requirements for empirical determination of Earth's climate sensitivity by S. E. Schwartz at the AAAS Annual Meeting, Denver CO, February 14-18, 2003

http://www.ecd.bnl.gov/steve/abstracts/Empirical.html). Most empirical determinations of climate sensitivity place it somewhere between 0.07 and 0.26 C/W/m2.

In contrast, the IPCC says a doubling of carbon dioxide will cause a warming of 1.5 to 4.5 C and have a climate sensitivity between 0.43 and 1.29 C/W/m2. They get these high numbers by assuming a number of positive feedbacks exist including changes in water vapor, cloud cover, and snow and ice cover. The water vapor feedback is incorrect and is discussed here.

3. The sum total of all feedbacks is assumed to be positive. Recent published work shows they are negative and these results are reviewed here.

4. IPCC economic models overestimate the rate at which carbon dioxide will enter the atmosphere over the next century. It leads to farfetched warming numbers such as 5.8 C. A critique is offered here.

5. Some easily modeled effects such as an increase in depolarization factor of air with more carbon dioxide are totally neglected in the climate models. Further discussion here.

Summary: Based upon the first three points above, the upper limit on warming due to a doubling of carbon dioxide is 0.7 C and it is probably much less. The high numbers used by the IPCC are not supported by measurements.


According to the surface measurements, climate has warmed by about 0.18 C/decade since 1979. Many people attribute all this warming to AGHGs, but alternative explanations exist. They are listed below with links to further discussion.

1. The sun may have warmed over the last 25 years and caused most if not all the warming as discussed here.

2. The albedo of the Earth has decreased (the planet is getting darker and absorbing more radiation). This will warm the planet and is discussed here. Land use changes are also discussed here.

3. Contrails have increased in recent years and will lead to a warming on regional and perhaps a global scale as discussed here.

4. Fossil fuel burning releases heat directly to the atmosphere and will cause a warming over the continents. It is discussed here.

5. Urban heat islands (UHI) are substantial (several degrees Celsius in many cases and larger than the predicted AGHG warming). Placing thermometers near cities and downwind of cities may lead to a warming that is falsely attributed to AGHGs. The effect is substantial and is discussed here along with a mention of land use changes. Further support that urban heat islands represent half of the reported warming in the twentieth century (0.3 C out of 0.6 C) comes by examining the changes in the diurnal temperature range (DTR).

6. Other explanations for the recent warming include:

a. Decrease in explosive volcanic eruptions in recent years.

b. Increased intensity of El Nino in the last few years.

c. More carbon aerosols (soot) in the atmosphere.

d. Soot on snow.

e. Decreased stratospheric ozone.

f. Internal changes in circulation such as the Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), and Arctic Oscillation (AO).


Starting in 1997, we created a scorecard to see how climate model predictions were matching observations. The picture is not pretty with most of the predictions being wrong in magnitude and often in sign. An updated version of the scorecard can be found here. It may be updated yet more depending upon the publicity that a claim receives or if readers send suggestions.