Warmer air has the capacity to evaporate more moisture into the air before saturation as compared to cooler air. When moisture is available such as from oceans, lakes, wet soils, vegetation, trees, etc. some of that moisture will enter the air through evaporation/transpiration. Not only can warm air have a much higher amount of moisture but liquid water is more likely to evaporation when the water and air are both warm. This is because the water molecules have more energy and thus it is easier for a water molecule to escape the liquid surface and evaporate into the air when it is warm. Warmer air is only one aspect of the air having a large amount of moisture. There also must be moisture available to evaporate into the air or moisture available to advect in. Warm deserts have the problem of not having much local moisture to evaporate into the air. Also, the transport of moisture is blocked from being brought in. This leads to less vegetation and even less moisture since vegetation can transpire large amounts of moisture into the air if it is present. A location that experiences both warm temperature and available moisture will generally have abundant vegetation, abundant rainfall, and humid conditions. The abundant vegetation and moisture sources help provide the air with abundant moisture. One consequence of global warming is that it should allow for more moisture to be evaporated into the air. This increase of moisture can lead to more clouds, rain and snow which help cool the air. Thus, this negative feedback loop may result in keeping a check on significant global warming from occurring. However, the increase of moisture in the air will help raise the air temperature further though since water vapor is a greenhouse gas. This positive feedback loop can help enhance global warming. These are only two examples of feedback loops and there are countless others that are all interconnected. This is one reason it is so difficult to know the future impacts of global warming. |