[dr_who]

What do they mean by global temperatures anyway? Assuming that the total radiant energy from the sun that is reaching earth is constant, how can air or water currents affect the average temperature? Seems to me that all currents do is move accumulated heat from one part of the earth to another unless these currents can somehow increase the total heat energy retention of the earth under certain circumstances.

[Old Professer]

Basically, you’re right; we have measurable regional temperatures and unmeasured interpolations — which are then added, averaged, adjusted and extrapolated for projections; and here we are.

[justa-hairyape]

Here is an example of how air can affect water temps at the surface. Take a close look at the Gulf of Mexico in the image below. It had been completely warmer then normal at least since summer. Notice how the Arctic air has cooled the Eastern Gulf near Florida and the Western Gulf near Texas. That just happened. Will probably be even cooler in the next days image. Someone posted on another thread how strange the waters off the Western coast of Florida looked yesterday from a jet landing in Florida. Steam was coming off the water. It was dramatically cooling.

Take a look at this animation. Note all the marine layer coming off the water in the Gulf and East coast of the US. That is because the air is much colder then the water. Our oceans are cooling. The sun moved the marine layer further off the coast by heating the air some, but late tonight the marine layer will be all the way to the coasts again.

Real-Time U.S. Composite Satellite Animation

[justa-hairyape]

And concerning the sun being a constant, it is not. Solar Activity varies quite dramatically across numerous vectors. Total Irradiance is not that important since the metric is screwed up by the nature of the sunspots themselves. The spots have a dark region that emits less light and a bright region that emits more light. So their affects on total emitted light are partially canceled. One of the real vectors one must look to see large scale variations is electromagnetic radiation outside the normal visible light spectrum (UV for example). It varies quite a bit. Also, solar wind, magnetic flux and cosmic ray interference are important vectors. And I am sure there are a few more that us apes is clueless about.

[palmer]

Assuming that the total radiant energy from the sun that is reaching earth is constant, how can air or water currents affect the average temperature?

The global temperature measured by satellite bounces around a lot. The basic reason is that weather (clouds, rain, water vapor, etc) is uneven and causes global cooling or global warming depending on how it adds up. It most certainly does not add up to zero, (e.g. the current freeze in the USA is not "balanced" by warm weather elsewhere).

As far as ocean currents and such, they cause global warming or global cooling on a slightly longer time scale. For example just a bit of extra wind across the Pacific (part of the ocean/atmosphere currents) will cause a great deal of extra evaporational cooling and presto, global cooling.