I have read that human mismanagement of land such as has occurred recently in China is responsible for much desertification. That seemed reasonable to me. There is, however, no compelling evidence that human emissions of CO2 have led to more droughts or more floods as alarmists like to claim IMO. Alarmists like to pretend to know our CO2 will cause more rain but it only occurs as floods. They could not allow in their cult something that might be interpreted as positive so any additional rain is in the form of floods (certainly not beneficial to plants or animals) and any drying is droughts. I also can't help but notice that clouds play a big role in weather too but since alarmists have a hard time blaming clouds on humans, the effects of clouds on precipitation are ignored as is the effects of warming on cloud formation.

Climate change is a very complicated matter, so to put it very simply, some of the things that are happening are:

Slightly higher air, soil, and water temperatures will increase the rate of evaporation. So if an area experiences higher temperatures throuout the year, it will always have slightly higher evaporation rates, making it drier. Secondly, higher air temperatures will allow the atmosphere to store more water vapor. The amount of water vapor that can be stored in air goes up, essentially, exponential with temperature. Therefore, when there is a precipitation event, more precepitation will occur at warmer air temperatures. Our greatest rainfall events are on hot, humid days, with less precipitation when it is cooler. Same for snowfall, the largest snowfall occurs when it is close to freezing, not when it is really cold.

Wind patterns and ocean currents determine the local climate. If an area tends to be wet, then the precipitation rates will probably go up (most of these areas are where wind goes across open water sources and then cools when reaching land). Most dry areas have dry air, so even if it does have a little more moisture in it, it will probably not reach saturation bcs the air temperature is also higher (and hence the water vapor holding capacity is higher).

I hope that helps.

I think it's a complicated problem and each region needs to be looked at on an individual basis. A couple of things that will change are the strength of the Hadley Cells and the position of the polar jet stream.Since the higher latitudes should warm more under global warming than the tropics, the temperature gradient will weaken. Temperature gradients are what drive mid-latitude storms, so that may be associated with the jet streams moving poleward (on average). The Hadley Cells--low pressure at the equatorial trough, high pressure at the subtropics--are what determines the arid regions of the world. From what I've heard, they will expand but grow weaker in strength. That can lead to situations where most years it's drier, but when they break down you can get occasional very wet years. That's what's expected for California, for example.

Note that even if precipitation amounts don't change, warmer conditions cause higher snow levels, which will cause water supply problems, since less water can be stored as snow pack.

Every weather system on Earth is driven by the presence of heat, if everything was balanced then there would be consistent weather at each point on the planet. Of course, it’s not at balanced and weather is a chaotic system (it’s weather that gave rise to chaos theory), it’s chaotic because of the imbalance of heat distribution.

As the amount of heat present in the atmosphere fluctuates (up or down) then it has a corresponding effect on weather patterns. For example, if there’s less heat then there isn’t the energy needed to drive atmospheric circulation and create monsoon cells. If it cools the monsoons fail and those places that would receive the intense monsoon rains now get less rainfall, the rain still has to fall somewhere but it’s no longer being carried by the cells and so is deposited in peripheral regions; hence some places get more rain whilst others get less.

The same principle holds true when the world is warming. Higher energy levels accelerate the hydrological cycle and energised weather systems can be moved further, in doing so the rains decrease in some areas and increase in others.

In general, not always, the dynamics of weather patterns that create arid or wet areas are simply enhanced by the presence of increased energy and thus wet places get wetter and dry ones become drier, a pattern that has been observed globally.

As Dr. Richard Feynman once stated in paraphrase "it doesn't matter how beautiful your theory is or who agrees with it; if it doesn't agree with experiment, it is wrong, period". The anthropogenic model is wrong, as is the theory since it requires the equatorial hot spot, which isn't there and all 73 GCM's have no skill in predicting future anomalies as well as feedbacks. With the lack of warming for the last 17 years, the manipulation of ground temperatures prompting warmers to state the last decade as the warmest on record, I am amazed that this religion is still going.

So far the skeptics have been correct in all of their assumptions and when a guy like Hansen comes forward and agrees there has not been any warming for 17 years yet many on this site continually strive to forward the sham. Interesting times we live in.

Actually, a warmer world would be advantageous to Mankind, animals and plants. Without the 5000 ppmv concentration of CO2 over 300 million years ago, most likely there would not be any complex plant life today. There is so much bad information on this site.

Ask the British Meteorological Office.

Wet places will become wetter and dry places drier, with droughts and floods, what is the basis of these statements, if there is a 5% increase in precipitation what why wont everywhere have 5% more snow or rain?

Actually we already know that through CO2 deserts are receding, more plants and trees more transpiration and holding of water, therefore more rain.