Extreme Weather, within the Framework of Climate Scientists
Extreme Weather, within the Framework of Climate Scientists
  • Reporter Park Do-won
  • 승인 2014.03.19 14:23
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FEATURE: Global Warming- What is Happening with the Weather?

Unprecedented abnormal weather climate events in history occurred this year without exception. In Egypt, it snowed the first time after 112 years. Killing cold snap struck across North America, and resulted in considerable casualties. Then, exactly what is unusual weather and how do scientists conduct research on it? The Postech Times looked at weather extremes in the context of climate change by interview with Professor Seung-Ki Min (SEE). This issue also includes information on CO2 emissions and the controversies of global warming.                                                               <Editor’s Comment>

Climate scientists’ ultimate goal is to prevent losses from weather and climate-related disasters by predicting future changes more accurately. They not only study changes in average climate conditions that occur over a large scale like global warming, but also changes in variability especially extreme weather (EW) events that usually occurs at local scale. With more frequent and stronger EW and consequential bigger damages, more and more scientists are working hard to understand the possible connection between EW and global warming.
EW can be divided into two aspects: temperature and precipitation. High and low extremes of the two variables -heat wave and cold snap, drought and heavy rains- do incalculable impacts on human society and ecosystem. For example, using the data observed over the past few decades, researchers investigated long-term changes in the highest and lowest temperature of each year. They found consistent increasing trends in extreme temperatures across the global land areas, in line with global warming. Although precipitation data are more limited than temperature data because of the local nature of its occurrence, intensifying trends in extreme precipitation were found over a large part of the global land area with sufficient data. This moistening trend is also in accord with global warming as more moisture becomes available in the warmer air.
People can easily accept fragmentary evidence for cause(s) of an EW delivered through the everyday media. On the other hand, climate scientists thoroughly verify such phenomenon utilizing all available data and known physical understanding. It is tough to clearly distinguish between natural range of fluctuation of the Earth’s climate and human-induced changes. For example, a deadly cold wave struck North America last winter and this extreme cold may look like a contradiction to global warming. However, there are now some scientific evidences that recent cold winters are partly due to Arctic warming which is related to sea-ice melting under global warming. In fact, such Arctic warming can induce a larger fluctuation of polar vortex (strong winds in upper atmosphere, trapping cold air within the Arctic circle), which in turn makes unusual cold air outbreaks into the mid-latitudes.
Interpretation of the same EW can also depend on data and methods. Therefore, scientists strive to get wider data pool and compare various analysis methods. Recently, researchers designed a new methodology, probabilistic approach. The idea is that human influence on a particular EW cannot be answered with a yes or no, but how probable it would occur with and without human activities can be examined. For this approach, computer climate models (hypothetic Earths) are used as a critical tool. By simulating many global climate models (GCMs, introduced on No.63 of The Postech Times) and assessing results in comparison with observations, climate scientists take a step forward more accurate understanding of past changes and thereby more reliable prediction of future changes.