Re: Ch. 5: The greenhouse effect
It would be superb if climate deniers would read just this chapter, which explains in simple physics why global warming is about as true as the ideas that the earth is round, about four billion years old and orbits the sun. The natural greenhouse effect increases the planetary temperature by 33°C. If earth had no atmosphere, like the moon, it would have the same temperature as the moon, since both are the same distance from the sun. The moon has an average temperature of -18°C. But the earth’s atmosphere works like greenhouse glass, allowing light in but not allowing heat to escape. This was discovered in the nineteenth century, when Swedish scientist Arrhenius used recently discovered laws of radiation to fairly accurately predict climate sensitivity to the doubling of CO2.
Wadhams provides a graph of satellite measurement of radiation at the top of the atmosphere, like this one from NASA https://www.giss.nasa.gov/research/briefs/schmidt_05/
(picture below). It shows how radiation would escape if earth had no atmosphere, and the actual escape rate, with big blockages at exactly the spots theoretically predicted by the study of the main GHGs – CO2, CH4, O3, N2O and H2O. The observation proves the theory. Denying this is like saying the world is flat – moronic.
The villainy of CO2 as the biggest GHG is compounded by how it sticks around for a thousand years, only very slowly removed by the carbon cycle. That is why geoengineering is needed. We have added about 640 billion tonnes of carbon to the air, and most of it will just stay there unless we work out ways to remove it. Ignoring this problem means getting a planet like Bill McKibben has just today described in the New York Review of Books – maybe 6°C hotter, in a situation where running a three degree temperature is a raging fever. https://www.nybooks.com/articles/2020/0 ... 0-degrees/
Wadhams says the only way to permanently get rid of CO2 is to bury it. That may be true, but less permanent solutions such as using carbon to make buildings and roads might be a better option. At least someone would then have the incentive to pay for the storage for centuries, which could end up being as good as permanent. Even what is known as ‘labile carbon’, such as biomass that quickly rots and returns as CO2 to the air, has an important role, since if we constantly increased the amount of planetary biomass by a trillion tonnes we would solve the climate problem. All it relies on is human beings having the brains needed to maintain ongoing regulation of the atmosphere, evolving to become truly sapient.
This chapter also explains that other GHGs – mainly methane and nitrous oxide – cause about 45% of the warming. The rocketing increase in methane seems to have slowed when Russia started caring more about pipeline leaks, and when the destruction of natural methane sources from wetlands accelerated. But that does not mean that destroying frog habitat is a way to stop global warming! A good brief summary is also given of the roles of ozone and the nasty artificial chlorofluorocarbons.
The key concept for climate physics is radiative forcing, the difference between incoming and outgoing radiation at the top of the atmosphere. RF doubled between 1980 and 2011, showing the rampant uncontrolled indifference of humans toward our planetary home. GHG levels define what is known as climate sensitivity, seen by the extraordinarily fine relationship over geological time between CO2 and temperature. Some calculations say the current climate sensitivity means we have stored up enough forcing to heat the planet by nearly 8°C, but Wadhams muses that those numbers are just too politically explosive to get a hearing in the UN.
The temperature rise naturally lags behind the forcing caused by extra GHGs, with most of the heat going into the oceans, but heat will inexorably catch up unless we remove the cause, all that past emissions, of which our new emissions each year amount to about 2%. Restricting climate policy to emission reduction simply ignores the main cause of global warming, the committed increase from past emissions. Wadhams compares the ocean to a temperature flywheel, now set in motion and with enormous momentum.
His section on The Recent Temperature History of the Earth shows the predicted rapid increase caused mainly by CO2 release, with a dip in the rate of increase caused by coal burning in the mid twentieth century, when so much polluting soot was released that it dimmed the tide of warming. The chapter concludes with an introduction to Arctic Amplification, which is the key terrifying problem of the world, considered objectively over decadal timeframe. Since 1850, the North Pole has warmed up at triple the rate of the rest of the planet, providing a bellwether for our global future. The main cause seems to be albedo, the farewell to ice, the fact that we are turning the pole from white to black with all our heating, from radiating reflector to heat absorber. All that heat that goes into the ocean warms the currents which flow through the Arctic, generating enormous warming forcing and a range of dangerous accelerating feedback systems.