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Climate Change vs. Global Warming

Climate Change is the preferred term to describe the rapid changing of the climate that we (the planet) are experiencing mainly since the 1900's. It is related to global warming.

Global Warming is the increase in temperature (generally) that has been occurring mainly since the 1900s. The issue, however, is not simply, that on average, the planets temperature is warming. Rather, if you agree that the climate will get warmer, then it makes sense that the warming will affect the water cycle and that in turn (coupled with a warming) will influence the climate. Global warming is the often used term, but not by my students who know better — climate change please!

What is the difference?

Not all the areas of the planet are likely to experience a warming, some areas will experience a cooling and so climate change is the preferred terminology. Also warming in some areas may prove beneficial but without water this benefit will be lost, alternatively if there is a change in the precipitation (rain, snow, hail, etc.) pattern as you would expect if the temperature changes, then too much or too little water can both be disastrous. Thus we are experiencing change, not just warming! Some plants will grow quicker and to a larger size, others will not grow, change is the key term.

The Greenhouse Effect

The greenhouse effect is a highly beneficial process where the planet is warmed by greenhouse gases helping to trap some of the radiation that would have otherwise escaped back into space. Without the greenhouse gases the surface temperature of the planet would be an average –18 °C (0 °F)! Chilly.

Greenhouse Gases

Source: United Nations Environment Programme / GRID-Arendal The greenhouse effect works because of IR radiation coming from the surface of the planet and IR absorbing molecules in the atmosphere. They absorb then emit IR in all directs a portion going back to the earth surface. Click here or on the image to see an enlarged view.

Greenhouse Gases are gases (in the atmosphere) that will absorb infrared radiation (learn more about the electromagnetic spectrum). Naturally released greenhouse gases include: water (H₂O), carbon dioxide (CO₂), methane (CH₄) & nitrous oxide (N₂O) (a.k.a. laughing gas). Ultra Violet radiation (UV) will penetrate the atmosphere and a portion will be absorbed by the surface of the planet. When radiated back into the atmosphere it will be in the form of Infrared radiation (IR), thus some of this IR radiation will be absorbed by greenhouse gases. Being a dumb molecule they don’t know which is up or down so after “doing their thing” they get “tired” and re-emit the IR radiation, a portion of which goes back to earth warming the planet. (Click here or on the molecule to see the molecule "Doing its thing".)

A molecule of Methane.

Providing the concentrations of the greenhouse gases remain the same, then other than normal seasonal temperature fluctuations the planet will have a relatively stable temperature year to year. Of course there are natural cycles in place that both remove and replace these greenhouse gases in the atmosphere.

Climate Change vs. the Weather

It is tempting on a very hot day to say: “that bloody global warming again!” But that would be incorrect. We do not say: “bloody ice age” on those very cold days (although predictions were made when I was a lad that we were about to enter a new ice age!) The weather is an event that is going to change and the temperature variations can be dramatic. Climate change occurs over a much longer time frame: at least decades! When we see a change in the average temperatures over the last 20 to 30 years then that is climate change. Climate change might influence the weather, stronger storms, more or less rain but single weather events cannot be attributed to climate change.

Daily mean maximum temperature and extremes for Pittsburgh, Pennsylvania

The average temperature for Pittsburgh is shown as the black line (middle), the red line (upper) is the high temperature and the blue line (bottom) is the low temperature. Clearly a wide variation of temperatures is possible within the high and low temperatures. Only the average temperature over long time periods will show any climate change warming (or cooling)!