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Into Climate Change
The Greenhouse Effect
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23 Articles
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Uncertainties in Greenhouse Gas Induced Climate Change

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Friends of Science advisor Madhav L. Khandekar wrote a report describing the uncertainties in greenhouse gas induced climate change and problems with climate models, dated March 2000. Since then the discrepancies between the climate model's hindcasts and the climate measurements have only grown larger. The mean surface temperature increase during 1978 to 1997 was 0.32°C, however, the impact of urbanization and land-use changes may have contributed about 0.1°C to that increase. The temperature trend in the lower atmosphere 1979-1998 was about 0.10°C/decade which is much less that the 0.16°C/decade at the surface, contrary to theory. The cause of the temperature change is a combination of natural variability including solar effect and anthropogenic sources. There are large uncertainties in radiative forcings by aerosols, which may offset a significant part of the greenhouse gas forcing, and in cloud and sea ice cover.

Correcting Flaws in Global Warming Projections

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Ron Clutz wrote a summary of a paper published posthumously of Dr. Bill Gray’s understanding of global warming/climate change. The global climate models (GCM) all project than an increase in CO2 warming leads to an increase in atmospheric water vapour. This results in the water vapour, which is a strong greenhouse gas, to cause further warming. In contrast to this positive feedback built into GCMs, Dr. Gray believes that there is a negative feedback, meaning that the temperature rise would be less than the direct effect of the theoretical CO2 warming. The paper says “CO2 warming ultimately results in less water vapour (not more) in the upper troposphere. The GCMs therefore predict unrealistic warming of global temperature. He hypothesize that the Earth’s energy balance is regulated by precipitation (primarily via deep cumulonimbus convection) and that this precipitation counteracts warming due to CO2.”

The Impact of Recent Forcing and Ocean Heat Uptake Data on Estimates of Climate Sensitivity

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Climatologists Nicholas Lewis and Judith Curry published an important paper in the Journal of Climate that estimates the climate sensitivity to CO2 using the energy balance method. Using the temperature history (HadCRUT4.5), ocean heat data and the most recent climate forcing information, the authors estimate the equilibrium climate sensitivity is 1.50 deg C, which is only 47% of the climate model average value. The likely uncertainty range is half of that estimated by the IPCC. The paper also refutes criticism of the energy balance method. While the paper does not address possible natural temperature recovery from the Little Ice Age, it concludes that the high values of climate sensitivity from climate models are inconsistent with the observed warming.

Climate Sensitivity from the Bulk Troposphere

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A new study by John Christy and Richard McNider used the warming of the bulk troposphere from satellite data to calculate an upper limit on transient climate sensitivity. The study removed ocean effect like El Nino and effect to two major volcanoes to determine a temperature trend attributable to only greenhouse gasses and natural forcing. If natural forcing contributed nothing, which is extremely unlikely, the temperature trend is 0.069 °C, giving a climate response of 1.1 °C, which is about one-half of the value estimate by climate models. A link to the paper is at the end of the article.

Estimating Climate Sensitivity Using Two-zone Energy Balance Models

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Empirical estimates of equilibrium climate sensitivity (ECS) can be obtained by comparing measurements of short-term radiation changes at the top of the atmosphere during the satellite era to corresponding changes in surface temperatures. Dr. Ray Bates from University College Dublin estimates ECS using a two zone energy balance model, where the radiative responses in the tropics (30 N to 30 S) and extratropics are estimated separately, and the dynamic heat transport from the tropics to the extratropics are explicitly estimated. Using likely ranges of the parameters from observations, he finds that the ECS is tightly constrained with a best estimate of 1.02 °C and a likely range of 0.85 °C to 1.28 °C.

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