1.The blue line shows the yearly average. If you look carefully you can see that there is a big spike in the global maximum in 1998 that dips back down in 1999 and then gradually increases upwards throughout 2000-2008. The 1998 spike is the reason some people say that global warming stopped in 1998. The spike was caused by El Nino. El Nino’s will push global temperatures up by approximately 0.01 degrees Kelvin (0.018 degrees Fahrenheit). In 1998 we had a much larger El Nino anomaly and the global temperature spiked much higher than that and then dropped back down to normal the next year. The blue line is flattening out from 2005 and I’ll explain that in the next picture.
This picture shows sun activity. The sun has been much colder than it has been in the past century since 2005. There is concern that we could be heading into a mini ice age if the sun continues to cool. But temperatures have not dropped because of the green house gas effect. If we go into a mini ice age the green house gasses might help mitigate it slightly. On the other hand, if sun activity picks up, we will be headed for an out of control warming that could end…we don’t know where.
Graph 3 shows changes in radiative forcing of climate since 1750. The zero line represents 1750. CO2 has increased overall radiative forcing by 1.5-1.75 W/m2. CH4 has increased radiative forcing by 0.8-1.2 W/m2. The sun (on the bottom), has increased overall radiative forcing by 0.05-0.3 W/m2. That is one tenth of the radiative forcing from carbon dioxide alone. The really big uncertainty we have is clouds. Climatologists believe that the overall cloud effect will be a cooling one. But, they are far from certain. Some clouds have a cooling effect and some have a warming effect and there are so many variables that go into what kind of cloud will be formed that it’s a huge uncertainty.
But there is no uncertainty over the fact that carbon dioxide and methane have increased radiative forcing by 2.3-2.95 W/m2 while the sun alone has increased radiative forcing by 0.05-0.3 W/m2.
The point of this graph is to show how big a role water vapor plays in the warming of the planet. And the hotter it gets, the more evaporation you get, the hotter it gets, the more evaporation you get...
It isn't only CO2 that's heating the atmosphere. CO2 could, at most, raise temperatures by 1.2 degrees C/K (1.96 degrees F). The problem is that in response to the 1.2 degree rise in temperature we get another 3 degree rise from water vapor. And as I said before, overall cloud effect is uncertain.
This graph shows three things.The black line is actual measured temperature anomolies. The blue line is an amalgamation of climate model predictions of temperature anomalies in the 20th century using only natural variables (sun, volcanoes, etc.). The pink line shows the results of the same models when anthropogenic forcings are added in (greenhouse gasses that warm the atmosphere and anthropogenic aerosols that cool the atmosphere).
This is basically the same thing but shows only ocean predictions.
This graph shows land predictions. If you look back and forth between the global land and ocean you will see that there will be much more warming over land masses. That’s because oceans store heat. We aren’t sure if and when the oceans will stop storing heat. At that point Global Warming will increase dramatically.