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Climate Change and Implications

Climate has changed in the past and will continue to change in the future. Climate change is a natural part of Earth's history. The issue is whether or not humans are significantly altering the natural progression of climate change, and if so, will these changes be detrimental to life on Earth, including human life. On this page we will examine the recent observed changes in temperture and climate as well as some of the impacts of those changes. We will then briefly discuss the IPCC 2007 report's estimation of what caused the recent observed changes. Finally, we will take a look at what could happen in the future if some of the predictions made by current climate models are correct.

Climate has changed during the past century. Below is a list of some of the changes that have occurred based on information contained in Climate Change 2007: The Physical Science Basis. Note that these changes are allegedly based largely on observations and to a lesser extent models, so we can place more confidence that these are correct in comparison to predictions of future climate change. However, some of the recent climate changes described in the latest IPCC Report are questioned by climate researchers. Please keep in mind that observed changes do not provide strong evidence for why the changes have happened. Arctic sea ice has decreased in coverage since 1980. We are quite certain of that. However, that observation does not prove that the reason for the decrease in Arctic sea ice is human emissions of greenhouse gases. A recurring message is that correlation does not prove cause and effect. For example, since 1980 we know that greenhouse gas concentrations in the atmosphere have increased and we also know that arctic sea ice has decreased, however the fact that these two events are correlated with each other cannot be used as proof that one caused the other.

Attributing Observed Climate Changes to Human Activities

The most recent IPCC report (2007) is now more forceful in its statement concerning the anthropogenic influence on observed climate changes: "Most of the observed increase in globally averaged tempertures since the mid-20th century is very likely due to the observed increase in greenhouse gas concentrations." This is different from the previous statement "most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations." The new assessment is said to consider longer and improved records and observations of climate change, as well as improvements in climate model simulations. Instructor's note: I wonder if they are putting too much faith in the ability of climate models.

Beside the International IPCC report, there are reports by US government agencies that claim there are climate change impacts that are already easily observable (e.g., see this EPA page on climate change indicators). In many of these reports, the reader is lead to believe, either explicitly or implicitly, that the climate changes mentioned are largely the result of global warming caused by human additions of greenhouse gases. First, it can be quite difficult to prove that climate has changed significantly given our incomplete knowledge of past climates and our incomplete understanding of how the climate system operates. Then on top of that we would need to prove that the climate changes were significantly influenced by higher levels of greenhouse gases. Most of the climate changes discussed in the EPA reports would be considered negative or bad effects of climate changes and end up being discussed in context of endangered species, forest resources, water availability, disaster planning, and the like. Often these possible bad effects of climate change are given as reasons to guide policy on greenhouse gas emissions in spite of the lack of scientific proof connecting them with increases in greenhouse gases. A skeptical view on some of the recent climate change indicators mentioned by the US EPA and attributing these changes to greenhouse gases is provied in Climate Change Impacts In The USA are Already (Not) Happening.

Climate is expected to continue to change in the future. The following list is based on climate model projected changes due to addition of greenhouse gases. Because this list is based on climate model projections, these changes are by no means certain to happen.

Potential Impacts of Climate Change / Impact Studies

Impact studies are done to try to understand how humans and other life will be affected by climate changes. This is really the ultimate question to answer. Unfortunately, we are not very good at predicting future climate changes, which makes impact studies uncertain. Most impact studies today are performed by models that first read as input the climate changes predicted by a climate model. Thus, if climate model projections for the future climate in a given ecosystem are wrong, then the projected impacts on that ecosystem will be wrong. Given the uncertainty in climate model projections, it is probably a good idea to perform impact studies on a whole range of possible future climates before deciding any long-term policies. Also keep in mind that even if we know for sure how the climate will change within a given ecosystem, it is still difficult to understand and predict how life within that ecosystem will adapt. Below is a list of some of the considerations within impact studies:

Please also read over this WORD document defining Impact Studies and Outlining possible consequnces of Global Warming. The figures and links below are from the EPA's pages on the impacts of climate change. As you might expect, this government website is biased toward possible negative impacts of climate changes resulting from human emissions of greenhouse gases.

[Potential Climate Change Impacts]


Health Impacts

Water Resources Impacts

Forest Impacts

Coastal Areas

Species and Natural Areas

Agriculture Impacts

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