Future Forecasts

Forecasting weather can have its challenges, and meteorologists are generally limited to a maximum range of between 11 to 14 days for making accurate forecasts of future weather due to the complexity and chaos of the system. Predicting future climate can be even more difficult.

Instruments such as rain gauges and thermometers allow a high degree of accuracy in measuring current weather conditions. In looking at past climate using paleo proxies such as tree rings and ice cores there is some degree of uncertainty in terms of how accurate the natural recorder is of the actual conditions at the time. Likewise, in forecasting the future, there are unknowns and uncertainties that scientists frame in terms of probability. Yet, communicating probability without using numbers is not easy. A statement such as "a high likelihood of drought conditions" is often translated as "there will certainly be a drought" in the media.

One question that many people are concerned with is whether or not global warming is occurring and what the consequences will be. We know from current research that the surface temperature of the Earth is warming, having risen by .6 degrees Celsius over the past 100 years. (See Whitehouse Press Release, June 2001). It is also known from ice core records from Lake Vostok in Antarctica that carbon dioxide emissions, primarily from the combustion of fossil fuels, are at the highest levels in over 400,000 years.

What remains uncertain is how these increases of carbon dioxide-- an important greenhouse gas-- and other human impacts such as land use changes will react with naturally occurring climate forces and variability in the future. Predictions of global temperature increases vary, but various modeling scenarios run for the Intergovernmental Panel on Climate Change ( IPCC) suggest a range of global warming of between 2.5–10.4°F by 2100. How these changes will impact regional climate and hydrologic dynamics is also largely uncertain.

For more on regional climate change, see the EPA's Global Warming Impacts and USGRP's Regional and Mega-regional Assessments from the National Assessment of the Potential Consequences of Climate Variability and Change which provide background on how potential climate change will impact water and other key resources.

Looking at the Past...Predicting the Future