When all you have is a hammer

There is an old saying that when all you have is a hammer, every problem looks like a nail. The trouble is that a hammer is a poor tool for driving in a screw and it doesn't work at all for tightening a nut.

Similarly, when your climate model begins and ends with greenhouse effect then it limits your vision. I've seen the people at RealClimate try to explain ice ages with no other mechanisms than CO2 emissions.

Here's an example of this taken to the extreme - using the greenhouse effect to explain Venus.

... But this was not always so, says Hakan Svedhem, an ESA scientist and lead author of one of eight studies published on Wednesday in the British journal Nature.

Venus, he believes, was partially covered with water before it became doomed by global warming.

"Probably because Venus was closer to the Sun, the atmosphere was a little bit warmer and you got more water very high up," he told AFP.

As water vapour is a greenhouse gas, this further trapped solar heat, causing the planet to heat up even more. So more surface water evaporated, and eventually dissipated into space.

It was a "positive feedback" -- a vicious circle of self-reinforcing warming which slowly dessicated the planet.

"Eventually the oceans begin to boil," said Grinspoon. "We believe this is what happened on Venus."
Even today, Earth and Venus have roughly the same amount of CO2. But whereas most of Earth's store remains locked up in the soil, rocks and oceans, on Venus the extreme heat pushed the gas into the air.

"You wound up with what we call a runaway greenhouse effect," Svedhem told AFP in an interview. "(It) reminds us of pressing problems caused by similar physics on Earth."

According to this theory, there were originally no significant differences between the Earth and Venus. This is no isolated article. Al Gore has said the same thing.

This overlooks a lot of things. Because of the inverse square law, Venus's closer orbit gives it twice the solar heat that the Earth gets. Venus does not have our moon which may have stripped some of the heavier gases from our atmosphere. And Venus does not have a magnetic field. As this article makes clear, the lack of a magnetic field allows the solar winds to change Venus's atmosphere.

“The solar wind interaction is important because it defines the conditions at the boundary of the atmosphere with space and it is a very active boundary,” says Stanislav Barabash at the Swedish Institute of Space Physics, Kiruna, Sweden.

In particular, the interaction causes Venus’s atmosphere to lose its gases in the form of ionized particles. The Analyzer of Space Plasmas and Energetic Atoms (ASPERA) on Venus Express has been studying this interaction and has revealed, for the first time, the composition of the escaping particles. They are predominantly hydrogen, oxygen and helium ions.

The hammer-only people miss a lot of important cosmology. This invalidates their model of the evolution of Venus and, by implication, Earth.

Since the hammer-only people only have one tool, CO2-based climate forcing, they over-estimate the influence that this has on the climate. This in turn causes them to see looming disaster. As the people who are yelling the loudest, they get the most attention - more than they deserve.