Global Warming Primer: Basic Physics Works, Even When Industry and Consumers Wish It Didn't
For decades, scientists have understood to at least a good ballpark estimate how much CO2 warms the atmosphere of Venus. It's only when global warming gasses are overtop industry and politicians that it gets complicated. This page attempts to frame the various aspects of scientific consensus and debate around global warming / climate change. Dealing with the headline of the day is much easier if you understand the basics and can place the headline into this context.
A brief history of global warming, based on type of science:
For perhaps half a century, the basic physics of what happens if we release CO2 and other global warming gasses into the atmosphere of a planet has been well understood. We couldn't model the details because we couldn't model the climate accurately ... but getting an overall estimate, looking at the overall heat exchange of the planet, CO2 increases clearly would cause warming. But fifty years ago, we did not know that CO2 would build up.
- The super-basics: The earth is nearly in balance, with heat (light) coming in from the sun matching heat radiated back into space from the earth, much like hot iron glows red, the earth glows infrared. CO2 is relatively invisible to higher wavelength light from the sun, and reflective of lower wavelength light radiated back out into space. Unless something very strange happens, increase CO2 and the air, water and/or land will get warmer. (The oceans, in fact, hold much of the heat -- which is a key part of why we can have an earth that operates on basic heat exchange physics but has different weather from year to year.)
1980s: Biology and Earth Science
During the Reagan years, the debate about global warming was different than today. Back then, deniers (this is from my memory) focused on the idea that increased CO2 would lead to increased plant growth and other absorption, and CO2 would not build up in the atmosphere.
1990s: Climatology and Statistics
CO2 did build up. It would take some pretty strange climate effects to counter the increased heat we knew was being reflected back. By the 1990's, the underlying science was getting much clearer, and the debate was getting less and less honest: the basic physics was clear, CO2 was building up, more heat/light was being reflected back to earth. But we could argue about climate models till we fry.
In a way, if we had no computers for climate models and no satellites for atmospheric measurements, global warming would have been "debate the details but no real argument it's happening" by the early 1990s.
Deniers have been using the rather odd argument that the earth's climate is unstable, that there has been warming in the past. But this argument only make sense if you believe in statistics, but not physics -- if we have an unstable climate and have added gasses that will cause increased heat/energy to our atmosphere and oceans, then we're taking an even bigger risk with our children's lives.
Other aspects of the debate are a form of bait-and-switch, for example putting the claim into the mouths of scientists that because GW gasses cause warming, ONLY GW gasses cause warming. Whether or not there was a Medieval Warming Period really is just icing on or off the cake to the basic physics.
2000s: Proof of Theory
In the last few years, we've seen a much more detailed set of evidence that basic physics works, even when industry and consumers wish it didn't.
* NASA can tell you how many watts per square meter are reflected back on the earth thanks to global warming gasses
* Measurements of the upper atmosphere match the predictions of energy being reflected back to earth by GW gasses.
* There is a warming trend that basically matches the GW theory.