http://cdiac.esd.ornl.gov/ftp/trends/co2/lawdome.combined.dat
1) Solar activity explains past changes in Earth's temperature.
No one challenges this notion. It's clear that before 1850, when the CO2 level was lower and essentially constant at around 280 ppm, solar activity was the main driving force in climate change. Before 1900, the CO2 concentration never exceeded 295 ppm in over 400,000 years. That's changed and now CO2 concentration is a bigger driver than solar activity.
http://cdiac.esd.ornl.gov/ftp/trends/co2/lawdome.combined.dat
2) Solar activity matches temperatures in the last 100 years better than CO2 concentrations, especially when temperatures dropped between 1940 and 1970, even though CO2 levels rose.
This is plainly false. Solar activity clearly increased between 1940 and 1960. Pollution during and after the war, when industrial activity was raised to unprecedented levels, caused temperatures to decline. Particulates and aerosols have a cooling effect by reflecting sunlight and by causing clouds to form. About 1970, serious efforts were started to control particulate emissions from fossil-burning power plants, and the temperature graph clearly shows that global warming accelerated. Furthermore, and more importantly, solar activity peaked in 1980, but temperatures have continued to rise. The only factor that can explain this is greenhouse-gas concentration.
3) CO2 levels lag behind temperatures by 800 years or so.
First, this possibility depends on proxy data, since records don't go back that far. But it could well be true because it's so consistent. If it is true, it's not good news. The proxy records show what you'd expect anyway: global warming causes greenhouse gases. Since greenhouse gases cause global warming (an inescapable fact of physics), we could face a compounding effect, where greenhouse-gas concentration and temperature reinforce each other all the way to the worst case. This is the possibility that causes the most concern.
4) Troposphere data don't reflect the same degree of heating as would be expected.
This is outdated, incorrect information. Here's a quotation from the Executive Summary of the Climate Change Science Program Synthesis and Analysis Product 1.1:
"Previously reported discrepancies between the amount of warming near the surface and higher in the atmosphere have been used to challenge the reliability of climate models and the reality of humaninduced global warming. Specifically, surface data showed substantial global-average warming, while early versions of satellite and radiosonde data showed little or no warming above the surface. This significant discrepancy no longer exists because errors in the satellite and radiosonde data have been identified and corrected. New data sets have also been developed that do not show such discrepancies."
5) Artificial emissions aren't sufficient to explain the increase in CO2 concentrations. Natural emissions are greater.
This is plainly false. Over 29,000 million metric tons of CO2 are emitted from artificial sources per year.[30] That is almost 1% of the amount of CO2 in the atmosphere, the concentration of which is rising roughly 0.5%/year. So, if 50% of the emitted CO2 stays in the atmosphere, it explains all of the increase. But it's true that other greenhouse gases are contributing as well.
6) Greenhouse gases are such a small part of the atmosphere they can't explain the temperature rise.
Oh, yes they can. The major constituents of air are nitrogen, oxygen and argon, which together make up 99.96% of the total, and these three gases have little or no greenhouse effect. We can do a quick calculation to show that greenhouse-gas concentration has risen enough to cause all of the detected temperature rise.
Return to the main page Global Warming: A Guide for the Perplexed
REFERENCE
30. http://www.grida.no/climate/ipcc_tar/wg1/519.htm
The world is facing some tough decisions on how to deal with the oncoming effects of global warming, so it's right and reasonable that people are looking at the subject closely to make sure we don't dislocate people's lives inappropriately.
In the past, this has led to some unfortunate situations. A few people claiming to have scientific qualifications have made arguments that are demonstrably false. It also led to an embarrassing TV presentation in the UK which claimed that global warming was a conspiracy authored by Prime Minister Thatcher in which scientists lied for pay. The presentation showed falsified solar data, claiming that it matched global temperature history, and warned that Africans would suffer severe deprivation if they were denied fossil-fueled electricity.
Among the skeptics, one of the most important is United States Senator James Inhofe, the ranking Republican member of the U.S. Senate Environment and Public Works Committee. One would predict that Senator Inhofe would examine the subject carefully. Representing an oil-producing state, and being a strong conservative with investments in aviation, the Senator also flies personal aircraft as an avocation. He and his staff have compiled an extraordinary treatise which must include just about every criticism aimed at the process by which the consensus on global warming was formed.
As we look through the arguments, some patterns emerge. The most substantive of the arguments assume that there can only be one cause of global temperature change; since solar activity was clearly the driving force before 1850, they conclude that it still is the sole driving force. This and the other scientific arguments repeat the false arguments mentioned before.
Of the remaining arguments, many contend simply that too much emphasis is put on dubious methodologies: proxy data and computer models. That's reasonable enough, but the compilation leaves out the fact that the proof of climate change doesn't depend on either of these, as shown in the main page.
Some of the critics don't challenge the science but complain about the management of the UN's Intergovernmental Panel on Climate Change. That's important to conspiracy believers but not to people more interested in the actualities.
The last group of critics don't challenge either the science or the politics, but warn that excessive alarmism could lead to mistaken decisions. Implicit in this argument is the contention that CO2's effects on the environment couldn't be very great.
The question here is, what is very great? We've only seen a temperature rise of 0.7ºC (1.2ºF) in over 150 years. Who cares? You can't even feel that! But mountain glaciers get a little less snow in the winter and melt a little faster in the summer. In time, the glaciers disappear and farmers who depend on snowmelt in the summer don't get it. Semi-arid parts of Africa that got just enough rain to grow some grass for cattle get less and tens of millions of people watch their livelihoods die. Beetles that never could get up a big population before because of winter-kill now can survive and increase gradually in numbers so they can destroy a forest. Cold-water fish don't tolerate temperature change and move to a different part of the ocean, disrupting their reproduction cycles. That's what we're seeing now: small temperature changes have big effects. What will happen as the temperature rises another degree? Or two degrees?
Maybe this is alarmism. If so, then alarmism isn't necessarily a bad thing.