Welcome to brain Stuff from How Stuff Works, Pay brain Stuff Lauren Vogelbaum. Here. You might remember when in Republican Senator James Inhoff of Oklahoma set out to refute the quote hysteria over global warming by tossing a snowball around inside the US capital. The obvious implication was, how could the climate be changing that radically from humans burning fossil fuels and pumping greenhouse gases into the atmosphere, since we still have snowfall and chilly temperatures on a winter day.
But even if you're not a U. S. Senator from an oil producing state, you might be wondering how it is that scientists can predict climate trends over many years but can't predict what the weather will be three weeks from today. The reason is that weather and climate are two very different things. Basically, whether it is what happens today or tomorrow or this week, it's the day to day variations. Climate, meanwhile, happens over many years. It's the
combined long term average of weather events. Scientists look at climate in terms of fixed thirty year periods. Right now, for example, scientists are comparing the daily temperature to the period that started in nineteen eighty one and ended in one. They'll shift forward ten years and start comparing temperatures to
the period between nine and twenty and so on. Scientists rely on thirty year periods because it's an amount of time that's long enough to produce meaningful comparisons, but just short enough that any changes that occur will be subtle without being imperceptible. Twenty years might not show enough change, and fifty years might be too drastic. To make sense of those, thirty year periods help us put the weather
on a particular day in the right context. Comparing the temperature on December to the same day a hundred years ago wouldn't provide that much useful information because the climate was too different then, but comparing it to the average of the temperature readings for every December five between nine and twenty ten, when the climate conditions were pretty much constant, makes it possible to say whether a given to number
five is an unusually cold or warm day. We spoke with Jonathan Martin, a professor of atmospheric and oceanic studies at the University of Wisconsin Madison. He explained or trying to compare apples to apples when it comes to prediction. Whether in climate are also very different. Weather forecasting, Martin explains, is based upon observation of conditions that are already occurring
in real time in the atmosphere. Because those conditions only exist for a short time, whether it can be reliably forecast only over relatively short periods of ten to fourteen days at most, though Martin said that's theoretical, My confidence ends at day eight. Envisioning climate, in contrast, is much more low resolution. Scientists are trying to project what the trend will be over a long period, not what the weather will be like on a specific day fifty or
a hundred years from now. That involves gathering and crunching huge amounts of data in powerful computers and doing modeling. We also spoke with Jeffrey S. Duke's director of the Climate Change Research Center at Purdue University. He said, in one sense, climate does not affect weather. It's a description of the weather over a long period. You could turn that around and say that climate provides you with information about how likely you are to get a given type
of weather at a given time of year. But historically the climate has been determined by the weather over long periods. He continued In another sense, though, climate for a given location is determined by a bunch of factors, such as the latitude and position on the planet, which affects how it is influenced by the circulation of the atmosphere and oceans, and the daytime heating of continents. Climate is also influenced by the composition of the atmosphere, the transport of water
from soil to air by plants, and other factors. On a given day, the sum of all these influences determines the weather, but as some of these larger scale factors change over time, they will drag the weather and the
climate along with them. In recent years, some of the sharp distinction between weather and climate has blurred slightly as scientists have used increasingly phisticated models and accumulated knowledge in an effort to figure out the extent to which some specific weather events, say a hurricane, a heat wave, or a monster snowstorm, is actually a function of climate change
driven by humans releasing greenhouse emissions into the atmosphere. By running thousands of computer simulations, they can conduct what if experiments, seeing how the atmosphere would behave if you removed one factor or another. Although such analysis is still a work in progress, Martin thinks that eventually it will be possible to determine the extent to which specific weather events are influenced by climate change. Some of that research is already
bearing results. The National Oceanic and Atmospheric Administration presented a paper in December in which they concluded that three extreme weather events in that year's record global heat, extreme heat over Asia, and unusually warm waters in the Bearing Sea would not have been possible without human caused climate change. Today's episode was written by Patrick J. Keiger and produced by Tyler Clang. For more on this and lots of other stormy topics, visit our home planet, how stuff Works
dot com. M