Climate Science, Risk and Solutions

• We know the effects of CO2 on the transmission of electromagnetic radiation and how this varies by frequency. Same for the other gases in the atmosphere.

• We know how much energy is coming into the system from solar radiation, which we also know accounts for almost all incoming energy. We know the frequency distribution of this energy.

• We can measure the outgoing energy, and see that there is an imbalance with incoming higher than outgoing.

• We can measure incoming and outgoing at the surface, and at various levels in the atmosphere, to track down where that net energy increase is ending up. Infrared is in the frequency range that CO2 blocks.

• We can measure incoming and outgoing energy at various levels in the atmosphere and measure temperature and see that blocking the outgoing infrared heats the atmosphere.

• We can see that this heating effect is a function of CO2 concentration, which he can observe is going up over time, and we can see that the amount of heating increase over time closely matches the amount of heating we would expect from the increasing CO2.

The above just takes lab work (e.g., characterizing how various gases affect radiation transmission), measurements of incoming and outgoing energy flow, spectrum, and temperature of the system as a whole (satellites can do this) and at the surface and at various layers of the atmosphere.

That shows that warming is occurring, and it is almost all due to increasing greenhouse gases.

That doesn't show that humans are responsible for this increasing gases. For that we have:

• Carbon comes in different isotopes. There is an isotope with a half-life of about 5700 years that is created in the upper atmosphere from cosmic rays and then spreads throughout the atmosphere. The other two isotopes common in the atmosphere are stable. By looking at the ratios of carbon isotopes in atmospheric CO2 we can determine that the large increases in atmospheric CO2 come from sources that have little or none of the radioactive carbon.

Living things and dead things that have not been dead for a very long time do have significant amounts of the radioactive isotope because living (this is the basis for carbon dating). That lets us rule out things like wildfires as a significant contribution to the increases CO2.

The major ways to get excess stable carbon isotopes in the atmosphere are volcanoes and digging up and burning fossil fuels. We know that most of the increase comes from fossil fuels rather than volcanoes or other geological activity because:

• We know how much fossil fuels are burned each year and so can calculate how much carbon that will release into the atmosphere and that accounts for almost all of the observed excess stable carbon.

• We can monitor volcanic activity and see that it is not high enough to be a major contributor. Maybe we've missed a lot of volcanoes or other geological sources, but if we have we know that they can't be omitting much because the ones we do know about plus the amount from our known fossil fuel use accounts for almost all of the observed excess.