Today's rapid population growth and technological advances have dramatically increased the demand on the Earth’s available water resources. Across the world, people, industries, and farms are exceeding the local supply of water resources. Use of fertilizers as well as industrial wastes have produced negative effects for the water (Internet source). Water is necessary to sustain life, and if humans continue the same practices of yesterday, there may be dire consequences to face tomorrow. As if these problems are not enough to deal with, there is an extra card that still needs to be put on the table…climate change. If the Earth experiences a rapid climate change due to anthropogenic sources, all aspects of the environment will be altered to some extent. The hydrological cycle, which is directly related to available water resources, would be altered by a climate change. However, the question to be answered is HOW will climate change alter the hydrological cycle? Although global climate change models have differing opinions on what the new climate will be like, they do agree that temperature and precipitation will increase (globally). If the temperature of the Earth increases, the evaporation of water will increase. This will lead to an increase of clouds and precipitation. These changes will directly effect agriculture, forestry, rivers, lakes, as well as the economy (Rind, et al). Due to these reasons, it is extremely important to address the issue of climate change and the hydrological cycle.
The evaluation of the hydrological cycle (hydrologies) were simulated using several computer models. The models used are the Goddard Institute for Space Studies (GISS) GCM for climate change, the CERES wheat and maize models, the FORENA forest dynamics model, and the Palmer drought severity index (PSDI) was used for water resources. Fifteen sights across the United States were used for the study, but only eight were examined because the wheat and forestry model were not able to grow anything at seven of the sights due to their location. For each site, the models were run with the current climate and a 4.5C increase in air temperature and a 4.5C increase in ocean temperature. However, precipitation was held constant (no change) for simplicity. The reason for using such a large increase in temperature is because it accentuated the results. It should be noted that the computer models all run using different algorithms to calculate the possible changes of the future. These different algorithms will produce varying results for the same parameter. However, it is more important to notice the TREND of all the computer models, than to take one computer model as being the correct one. For example, we believe the temperature of the Earth will increase because all the GCMs predict a higher temperature, although they disagree as to the extent of the increased temperature.
The results of this study are very interesting, but leave many more questions to be answered. In summary, evaporation was generally agreed to increase from 2% to 18%, while the GISS GCM expected a 1% decrease. Runoff is expected to decrease from 9% to 46%. Soil moisture is thought to decrease from 2% to 35%, although the maize model expects a 0.5% increase. Finally the potential evaporation (PET) was measured. PET is the maximum amount of evaporation possible in any given circumstance. It is expected to increase by 16% to 48%.
The presented material show large differences in the expected future changes, and we must ask ourselves why. Can runoff be accurately calculated with coarse vertical and horizontal resolutions? What is the best formulation for PET? What time of year will the majority of the future changes take place? How accurate can the models be assuming no change in precipitation? Is it accurate to assume the ocean will increase by 4.5C if the atmosphere does? Furthermore, some of the inconsistencies are due to the different resolutions used by the models. For these reasons, the researchers admit that more needs to be done in order to fully understand the climate change-hydrological cycle impacts on the Earth. Furthermore, the article suggests that climate change professional and climate change impact professionals work closely together to produce more useful results to better understand the hydrological cycle and what can be expected of it in the future.
Overall, this article was an excellent one. Not only did it present good information about the potential future of the hydrological cycle with climate change, it also revealed some of the models weaknesses. For those reasons, this article was very professional and well thought out. I was impressed to see skepticism among the researchers in this article because the last two articles reviewed were not so skeptic. Hopefully more research will be done in this area so we can better understand the human impact of the hydrological cycle and global climate change.
References
"The impacts of climate change on water resources". Iowa State University Agronomy and Atmospheric Science Departments. http://www.unep.ch/iucc/fs104.html.