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Understanding climate change

Climate Change 

Infra red emissions from warm bodies was first identified by Herscel in the 1850's. By the 1880, infra spectra had been measured.









Famously in 1902, Svante Arrhenius published a paper identifying the hazards of fossil fuel use, was picked up by the popular media. His critical observation was that carbon dioxide absorbs the infra red black body emissions from a 20C earth. 

In 1988, James Hansen, then the director of the NASA Goddard Institute for Space Studies, stated to the U.S. Senate Energy committee “The greenhouse effect has been detected, and it is changing our climate now.” 


The Vostoc ice cores taken from Antarctica, show the carbon dioxide in the air tracking temperature through the ice ages, the second  graph shows the recent rapid increase in carbon dioxide way above previous concentrations since 1900.  



By 2022, the impacts of climate change were affecting every corner of the earth through extreme weather and changes in the distribution of water. For example, major rivers are drying out, glaciers disappearing, along with  massive floods.






The measured greenhouse effect shown in the graph below is around 1C per 100 ppm in CO2, in spectacular agreement with Arrhenius's original estimate of 1.3C







The current projections suggest that by 2100, there could be a 5C  increase in temperature, and a 5 ft rise in sea level.

The effect of carbon dioxide on temperature takes around 500 years to reach equilibrium, with an additional 1-1.5C over the "immediate" impact.

The effect on the equilibrium sea level can be estimated based on what happened 100M years ago in the time of the dinosaurs. Carbon dioxide was 700ppm above current levels, temperatures were 10C higher, there were no ice caps and sea levels were a stunning 100m (330 ft) higher than today. 

NASA climate database 

If all the ice covering Antarctica, Greenland, (Antarctica would make about 60 meters of sea-level rise, Greenland about 7.4 meters), and in mountain ice caps around the globe were to melt, sea level would rise about 70 meters (230 feet) and cover all seaside cities.

Antarctic ice sheet weighs 24,380,000 gigatons, that is being lost at  40 ± 9 Gt/y from 1979 to 1990, 50 ± 14 Gt/y from 1989 to 2000, 166 ±18 Gt/y from 1999 to 2009 and finally 252 ±26 Gt/y from 2009 to 2017 for a roughly 1C rise.

For a 10C rise, a simple linear extrapolation suggests  thousands of years to get to equilibrium ice levels for a given temperature.  

In the short term it is estimated that by 2100 the rise could be 2m, probably 20x higher when ice melt equilibrates after 500+ years. These sea levels will force relocation of most sea edge cities in the world. The time scales emphasize that the changes we have seen already are nothing compared to what will happen as we reach equilibrium, and also how long it will take for the changes that we must make will have an impact. 

Greenhouse spectra.png
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