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I got this one from the forums a couple of days ago.

Could you please elaborate on how exactly Global warming affects the wind causing changes in their patterns? I was unable to find a direct relationship between the two. I would be glad if you would let me know.
Thanks and Regards
Sujata

Thanks for your question Sujata. Lets start by talking about where wind comes from. The earth is a complicated place, lots of factors and lots of forces making things go all day and all night. That’s part of the reason its so interesting to live here. There are some things however we have discovered over the years. You most likely already know that the earth is tiled slightly along its axis, and that it goes around the sun. This means that different parts of our planet get different amounts of sun light. Among other things this tilt and solar orbit cause the seasons. It also causes the wind.

Because of the tilt, and the seasons, different parts of the earth are warm and cold at different times. If one part of the earth is warm (say the equator) and another part is cold (say the north pole) the air at the equator will warm up, warm things rise, so the air will start to rise up towards the sky, at the same time however because the earth is turning and because the earths gravity keeps the warm air from flying into space that air will start to move, this is wind. Wind is actually stored up solar energy. If we build wind turbines to capture the wind and make energy, we are really capturing solar energy that has been transformed into wind energy.

All the mountains, oceans, valleys and whatnot effect the way the wind goes, but for the most part these large scale patterns develop and stay pretty consistent. You have to remember that wind patterns are driven by the difference in temperature between different parts of the earth, the temperature difference between the surface of the earth and space, and the turning of the earth. It can get complicated fast.

So how does global warming figure into this? Global warming is causing a lot of the parts of the earth to get warmer. The poles are warming very fast, as are the oceans. So that means that places that used to be cold are now getting hot. So in some cases global warming is making wind patterns weaker. Because the difference in temperature is less the wind will blow less. This has a lot of consequences.

Winds carry water from wet places to dry places, so a low rain area becomes a desert when the wind doesn’t blow as often. It could also mean that an area that is somewhat dry because the wind is blowing the water away, might suddenly flood if the winds slow down. This is going on right now in the pacific.

Global warming caused by human activity has begun to dampen an important wind circulation pattern over the Pacific Ocean, and that could alter climate and the marine food chain in that area, a new study suggests.

It’s not clear what climate changes might arise in the region or possibly beyond, but the long-term effect might resemble some aspects of an El Nino event, a study author said.

El Ninos boost rainfall in the southern USA and western South America and bring dry weather or even drought to Indonesia, Malaysia and elsewhere in the western Pacific.

As for the Pacific food chain near the equator, the slowdown might reduce populations of tiny plants and animals up through the fish that eat them, because of reduced nutrition welling up from the deep, said the author, Gabriel Vecchi.

The slowdown was detected in shipboard and land-based data going back to the mid-1800s. It matches an effect predicted by computer climate simulations that trace global warming to a build-up of heat-trapping greenhouse gases, the researchers report. But simulations that consider only natural influences fail to produce the observed slowdown, Vecchi said.

So, it appears the slowdown is largely due to the man-made buildup of greenhouse gases, the researchers concluded. And the result lends more credibility to computer models that trace global warming to greenhouse gases, at least for their ability to forecast what will happen in the tropics, Vecchi said. (via)

You will notice that they also talk about ocean currents. Wind currents are a big driver of ocean currents. Ocean currents also have a lot to do with the weather. So changes in wind currents, change ocean currents, which further changes which parts of the earth are warm and cold, which effects the wind more which effects the ocean… you get the idea.

So global warming can slow wind down, because it lowers the difference in temperature between one place and another (mostly by making cool places warmer). Here is a picture of the warm gulf stream ocean current going up into the cold north Atlantic (remember ocean currents are pushed around by wind currents).

You can see how ocean currents move heat around the planet. In this example the gulf stream moves heat from the tropics up around Florida (making Florida very warm) and then jets off like that into the north Atlantic. This is why The UK has the climate it does. Without the warm waters from the gulf stream (and other ocean currents) the UK would be much colder than it is. Get out a map and draw a line from England over to Canada, and you will see they have very different climates, but are about the same distance north. All because of ocean currents and wind currents.

If wind currents were to stagnate it could radically change the climate. Warm places might become very warm, or they might suddenly get very cold, wet places could get dry or flood. Our system is a delicate balance, throwing it out of balance will have very hard to predict consequences.

There is one last thing that I have not talked about, the global conveyor belt (the Thermohaline circulation). Not all ocean currents are driven by the wind. There is one very large and very important current that is driven by wind, and salt.

This current is kind of special, it regulates the temperature of the planet, it keeps the warm parts from burning up and the cool parts from freezing solid. Some scientists even think that it was the stabilization of this great current that helped to keep the planet from continuing on its ice age/hot age swing ten thousand years ago.

Extensive mixing therefore takes place between the ocean basins, reducing differences between them and making the Earth’s ocean a global system. On their journey, the water masses transport both energy (in the form of heat) and matter (solids, dissolved substances and gases) around the globe. As such, the state of the circulation has a large impact on the climate of the Earth.(via)

The belt is also special because of the way in which it is driven. It moves around because of differences in the salinity of ocean water. Warm less salty water is less dense so it “floats” up. Salty water is more dense and so it sinks. This rising and sinking causing currents. In the same way that the differences in temperature can cause wind currents to flow, differences in salt content can cause ocean currents to flow. Saline differences do not move the water around the planet very fast, in fact this current takes a very long time to make one trip around the world, over 2000 years.

As the Greenland ice sheet melts due to global warming it is pumping a lot of fresh water into the north Atlantic (if you take a look at that picture you can see the belt makes a loop through the Atlantic). As this fresh water collects it will slow down the sinking of the salty cold water (because the water will be warmer and fresher), and may stop the conveyor belt altogether. If this happens the wind currents that used to pick up warm moist air from the gulf stream currents (the ones that keep the UK warm) might start to pick up cold air. This could have the effect of freezing out parts of Northern Europe. Meanwhile the heat that the current used to take away from the tropics would stay put causing the tropics to burn. Check out this animation to see what I mean.

So global warming can both effect the strength of wind currents, as well as the temperature of wind currents. Making our climate less predictable, and a lot less pleasant. I hope this helps you understand the link between the temperature of our planet and the wind currents.