Global Warming versus Climate Change

What’s the difference ? Why is Global Warming not the same as Climate Change ? And why do we call Global Warming “anthropogenic” ? How do we know recent Global Warming is caused by mankind’s activities ?

So, what is Global Warming ?

1. Carbon Dioxide is a Greenhouse Gas

Without Carbon Dioxide and other Greenhouse Gases in the Atmosphere (air), the temperature at the Earth’s surface would be something like 30 degrees Celsius colder than it is now.

This is a well-established fact, about which there there is no dispute. Well, OK, some people dispute it, but the fact that they dispute it does not alter the data.

It’s also a well-established old fact : the original science about the Greenhouse Effect was done over 100 years ago :-

http://www.aip.org/history/climate/
http://www.aip.org/history/climate/summary.htm

For those who missed it, David Archer’s University of Chicago class on “Global Warming for non-science majors”, online, free of charge, is an excellent introduction to the basic Physics :-

http://geosci.uchicago.edu/people/archer.shtml
http://geoflop.uchicago.edu/forecast/docs/lectures.html

David Archer’s approach is non-threatening, accessible and clear : the Greenhouse Effect is what keeps the temperatures at the surface of the Earth habitable. And Carbon Dioxide is currently responsible for around a quarter of the warmth.

You increase the amount of Carbon Dioxide in the Atmosphere, the planet gets hotter. That’s Global Warming. And that’s a fact. An indisputable fact. Yes, yes, OK, well some people do in fact dispute that more Atmospheric Carbon Dioxide makes the planet hotter. But they don’t tend to be climatologists, paleoclimatologists or paleogeologists, so I wouldn’t recommend paying any attention to them.

2. Carbon Dioxide levels in the Atmosphere are rising.

3. The isotopic signature of the Carbon Dioxide that’s increasing in the Atmosphere points to mankind’s combustion activities.

4. John Cook has a nice post that explains the rest, with diagrams :-

http://www.skepticalscience.com/human-fingerprint-in-global-warming.html

So, why is Climate Change different from Global Warming ?

1. Climate Change is a collection of effects that happen when the average temperature of the Earth’s surface rises.

2. Some of these effects are called “feedbacks”, as they can cause extra Global Warming. One example is in the Arctic region, where Global Warming effects are causing meltdown of the ice and surrounding permafrost. The melting ice and warming permafrost cause changes that mean more warming.

3. Just how sensitive is the Earth to Global Warming ? And how much extra Global Warming is happening because of the changes to the Earth caused by Global Warming ?

“Climate Sensitivity” is a hot topic. It could be “lots” or it could be “some”. Most of the current science is about how to read the changes in the Earth, and model what could come next. The computer models give projections that are matched against what is actually happening.

Some calculations of “Climate Sensitivity” are based on research into what happened a long time ago in Earth history, so it’s not all about models.

So in summary, you can see that Climate Change is a kind of shorthand for “Global Warming causes things that cause more Global Warming”.

Some research on Climate Sensitivity :-

http://www.skepticalscience.com/climate-sensitivity.htm

http://www.skepticalscience.com/news.php?n=193

http://web.mit.edu/newsoffice/2010/explained-climate-sensitivity.html

http://iopscience.iop.org/1755-1315/6/1/012023/pdf/1755-1315_6_1_012023.pdf
(A “GCM” is a “General Circulation Model”, “General Coupled Model” or “Global Climate Model”. Whatever “GCM” means to you, what it does mean is a heavyweight computer programme.)

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