Seattle Times: "The truth about global warming"

What a great ski year!  Snow all over.<br><br>It bothers me a little that scientists have presented us with the simplest conclusions that make for good new stories.  I prefer to look beyond the headlines.  <br><br>In searching on the internet, I find one of the useful keywords is "anthropogenic", literally meaning 'human generated', as in anthropogenic warming, anthropogenic climate change, etc.<br><br>In reading one interesting article, Climate Change and Greenhouse Gases , at: www.agu.org/eos_elec/99148e.html

....my own conclusion is that while co2 effects are fairly predictive, there are other factors that are less understood to the point that there is a significant amount of uncertainty to predicting climate change.  So, while citing this article to highlight the element of uncertainty, I would agree that moving to control co2 emissions is probably a good idea.  However, I am not prepared to panic just yet.  In posting part of this article, the bolding of text is mine, in order to highlight that there is more uncertainty than is related in newspaper and television stories.  Perhaps we have locked onto co2 effects because it is the only factor that we can claim to understand.

.....A principal source of uncertainty in modeling climate change during the industrial period arises from uncertainties in the representation of the influence of anthropogenic aerosols. Aerosols scatter and absorb short wave (solar) radiation and modify the reflectivity of clouds. Both effects are thought to decrease the absorption of short wave radiation by the Earth, exerting a cooling influence on climate, despite the fact that tropospheric aerosols are short lived in the atmosphere (a few days) [Charlson et al., 1992; Kaufman and Fraser, 1997; Twomey et al., 1984; Haywood et al., 1999]. <br><br>Recent climate modeling studies which include the effects of aerosols [Hasselmann, 1997; Hegerl et al., 1997; Houghton et al., 1995; Kattenberg et al., 1996; Mitchell et al., 1995; Roeckner et al., 1996] show improved comparisons between the simulated and observed global temperature trends during the industrial period. However, given the present large uncertainties in aerosol forcing, such improvement may only be fortuitous. <br><br>An additional uncertain contribution to radiative forcing of climate change during the industrial period arises from possible changes in solar irradiance. Based on reconstructions of solar irradiance and climate response in the preindustrial era, together with instrumental records and solar observations during the industrial period, Lean and Rind [1998] estimate that solar forcing may have contributed about half of the observed surface warming since 1900. <br><br>Uncertainties regarding clouds and the hydrological cycle and their representation in climate models also introduce uncertainty into present understanding of the response of the climate system to increases in atmospheric greenhouse gases. It has been indicated in model calculations that warming in the lower atmosphere as a result of greenhouse gases would increase the abundance of water vapor in the atmosphere and intensify the hydrologic cycle [Gates et al., 1992; Kattenberg et al., 1996]. <br><br>These changes might be expected to lead to an enhancement of cloudiness. Clouds reduce the net absorbed short wave radiation in the climate system because of their high reflectivity (a cooling influence); however, they also radiate energy back down to the surface and lower atmosphere (a warming influence). The overall effect of these opposing influences is a net cooling [Ramanathan et al., 1989] although this varies regionally, with cloud type, and with geography. The question of whether average cloudiness would be increased or decreased in a greenhouse-enhanced world is not yet established. Issues such as these contribute to the present uncertainty in climate sensitivity. <br><br>Summary <br><br>In summary, the atmospheric concentrations of the principal anthropogenic greenhouse gases (CO2, CH4, N2O, CFC-11, and CFC-12) have increased significantly during the industrial period. Elevated concentrations are predicted to persist in the atmosphere for times ranging to thousands of years. The increased atmospheric levels of these gases, especially CO2, increase the IR energy absorbed by the atmosphere, thereby producing a warming influence at the Earth&#8217;s surface. <br><br>Global mean temperatures have increased between 0.3 and 0.6° C during the last 150 years. This change has not been monotonic, but it is unusual in the context of the last few centuries. On the timescale of the last few thousand years there have been larger climatic variation during times when variations in CO2 have been relatively low. It is clear that atmospheric CO2 is not the only influence on global climate. However, there have been large natural variations of CO2 in the geologic past, and these changes are correlated with general features of climate change. There is no known geologic precedent for large increases of atmospheric CO2 without simultaneous changes in other components of the carbon cycle and climate system. <br><br>Changes in the climate system that are confidently predicted in response to increases in greenhouse gases include increases in mean surface air temperature, increases in global mean rates of precipitation and evaporation, rising sea level, and changes in the biosphere. Substantial uncertainties remain in the magnitudes and geographical distribution of these changes and in the rates at which they may be expected to occur. The significant recent progress in the scientific understanding of climate change and the uncertainties in predictions of climate change are documented in the peer-reviewed literature. Peer-reviewed scientific research provides the scientific basis for the AGU position statement on Climate Change and Greenhouse Gases and must continue to be utilized in informed decision making on this issue. <br><br>  

Good points on uncertainty, which of course cuts both ways (could be less bad, could be worse than expected...). Here's a recent item from the Washington Post (I avoided some more liberal-slanted news outlets for this story, which appeared in similar forms throughout the various media, though this one quotes conservative darling George Taylor as part of its effort at "balance"):<br> www.washingtonpost.com/wp-dyn/content/ar...AR2006030201712.html

They key piece of this story is that at least this one research finding suggests that the melting down south is going a lot faster than most models have predicted. Another media reference to this quoted some scientists as saying it will force them to work up new models that account for this. Uncertainty indeed.

In the meantime, at least the oft-mentioned geographic variability to warming seems to have favored us PNW skiers this season.

I read somewhere awhile back that Mars is going through its own global warming. I wonder who is to blame for that?

Nice galactic logic. And I think the sun is cooling off too, so how could the globe be warming??

An interesting lead story in Scientific American, March 05, suggests early land clearing and rice cultivation began staving off a beginning ice age 8,000 years ago. Unfortunately one has to subscribe to read the article, but this link leads to the course material described.<br> mac01.eps.pitt.edu/Courses/GEOL1055/Ruddiman_2003.pdf
Fairly technical reading but some of the evidence used to support the arguement is also enlightning. That section begins on page 20.

An article today:<br><br>Experts forecast another active Atlantic hurricane season<br>Apr 04 11:03 AM US/Eastern<br><br> www.breitbart.com/news/2006/04/04/060404150343.0ufe6r2g.html

Excerpt:

Some scientists also believe global warming plays a crucial role by further increasing the temperature of warm ocean waters that provide fuel to the hurricanes.

But the Colorado State University study played down the theory.

"No credible observational evidence is available or likely will be available in the next few decades which will directly associate global surface temperature change to changes in global frequency and intensity," it said.