Two things:
1. Temperature fluctuations can be precisely reconstructed using the main climate forcing mechanisms.
These are: external (solar input) and internal (volcanoes). This is aside from any anthropogenic (human) "meddling" in the form of aerosol or greenhouse gas emissions.
Since we have had meterological observations we can compare what the climatologists have reconstructed (temperature with high accuracy and precision and precipitation with less accuracy and precision) with the actual temperature measurements and observations.
From ~ AD 1600 (beginning of observational record) until the inception of the industrial period, the predicted (reconstructed) temperatures are precisely what is predicted/reconstructed by the model using the natural climate forcings of solar input and volcanic activity. However, since the industrial period, the temperature record can not be modeled using solar and volcanic forcing. Only by factoring in the re-radiative influence of greenhouse gases- carbon dioxide and methane, but others as well- can the temperature be accurately reconstructed.
The interannual variability (up and down wiggles of temperature like, 1998 being hot and 2005 being colder, etc) is the same in *frequency*, but the *magnitude* is too low if you do not factor in greenhouse gases. It is like the same temperature curve is shifted up a "notch" from what it would be with out anthropogenic warming.
This is why it is rediculous to say that, oh- since this year is colder than 1998, then "global warming" is not happening. You need to look at what the trend would be *with* ghg factored in and what it would be *without* anthropogenic forcings.
And the tired argument that earth goes through natural cycles... Yes, it does, we know the magnitude of the greenhouse gases for these cycles for the last 800,000 years. Than is almost a *million* years. There is a maximum and a minimum that correspond to glacial maxima and minima. We are currently orderrs of magnitude out of that range. and teh levels have increased at a rate (rates are important in biology and climatology) that is entirely unprecedented- which is undisputed. Now, can the Earth survive that corresponding temperature increase? I don't know. We will find out. But the fact that GHGs are higherr than they have been in almost 1 million years, and that warming can be attributed to them is undisputable.
Which brings me to point two.
2. The "consensus issue". For my PhD I am getting a minor in Global Change (it has always been called global change, not global warming, as the effects of an altered climate include increased temperatures but also changing precipitation and atmospheric circulation etc -the media just like "Global Warming", it sounds scary) and we wanted to find a climate change contrarian to come in to talk to our class. The *only* one we could find - that is on "the list" (of scientists that disagree with global change ideas) was a professor in the Atmospheric Sciences department- we were excited!! cool!
So, come to find, he was put on the list because.... he disagreed with the magnitude of the change predicted for *precipitation* (that's rainfall) in the southwestern US. What ?? didn't he disagree with climate change???
no.... He, like the rest of the climatology and paleoclimatology community understands the physical mechanisms behind the increase in temperatures attributed to recent rises in carbon dioxide. The findings are robust and have been repeatedly tested and he understands that. He just had a problem with the findings of the IPCC (Intergovernmental Panel on Climate Change) on the timing of rainfall...
Important lesson for those who look at that list, don't ya think? Many are scientists from fields faaaaar from climatology and those that are in the field, like Dr Castro, don't disagree with the fact that the Earrth is warrming due to anthropogenic reasons- the compilerrs of the list *cherry-picked* (like the WTBTS, guys) statements that put them at odds withthe IPCC...
-K
