Because the Earth's climate is a huge, complicated system of many components (such as atmospheric temperature, humidity, wind systems, ocean currents, and the influence of topography) at many different scales (local, regional, and global), there are many things scientists do know about global warming, but there are also some things they still do not know.
According to the EPA there are three things scientists do know about global warming.
1. They know for certain that human activities are responsible for changing the composition of the Earth's atmosphere. The increas ing levels of CO2 and other greenhouse gases in the atmosphere since the preindustrial period have been well documented. There is nothing other than human activities that can explain the addition of these additional greenhouse gases.
2. Scientists clearly understand the greenhouse effect. They know that the Earth's natural greenhouse effect is vital for life to be possible on Earth. They also understand that human activities are adding additional CO2 that enhances the natural effect and raises temperatures. Through experiments, they also know that the CO2 that humans add can stay in the atmosphere for centuries.
3. Temperature records kept since the late 1800s have enabled scientists to determine that the atmosphere has warmed an average of 1°F (0.6°C) over the past 100 years worldwide, except in the polar regions where it has experienced an even greater rise. This is supported by much evidence: glaciers are melting, snow cover in the Northern Hemisphere is melting, and regions with permafrost are starting to thaw.
Sometimes scientists classify things as "likely but not certain." This leaves the door open for further evidence to be collected to either lend credence to the theory or not. Based on the EPA's findings, scientists are not certain how much warming can be attributed to human interference and how much has been contributed by natural factors because the interactions of multiple variables, both anthropogenic and natural, are so complex. It is like untangling a strand from a giant web. Research in this area is incomplete.
It is uncertain how much and how fast the Earth's atmosphere will warm. The IPCC has projected a 2.2-10°F (1.4-5.8°C) increase by the year 2100, but they cannot say with any certainty how much it will warm by a specific time period.
There are also things scientists admit they do not know about global warming. Scientists have not been able to predict, for example, the precise effects global warming will have on individual communities—they have only been able to describe regional effects with accuracy. Predicting changes in temperature, rainfall, water supply, and soil moisture for local areas is not possible at this time. They also have not been able to predict specific impacts on local health, forests, wildlife, resources, agriculture, and water supplies due to global warming. One of the reasons this is so difficult to predict is because computer models have not progressed far enough to analyze small-scale local effects; they work better at large-scale global effects.
Another source of scientific uncertainty stems from the fact that complex systems inherently have unexpected surprises associated with them and are usually hard to predict and account for ahead of time. Major uncertainties include:
• How much more warming will there be?
• How fast will the warming happen?
• What will be the adverse effects?
• Will there be any beneficial effects?
Scientists have learned to deal with, and accept, uncertainty. Uncertainty leads to more research, which ultimately leads to discoveries and better understanding, offering a new framework to operate in and advance.
Was this article helpful?