Reading 2

Unit 5-Reading 2

Page 74

Weather, Climate, or Both?

In the summer of 2010, parts of eastern and southern Europe baked in temperatures they had never experienced before. Ukraine saw its highest temperature ever recorded—106 3 degrees Fahrenheit (41.3 degrees Celsius)—and the island of Cyprus recorded an air temperature of 115.9 degrees (46.6 degrees C). As the core of the heat moved over Russia, about 15,000 people died. Many people interpreted the brutal heat as evidence that the climate of Earth really has changed, that the phenomenon known as global Warming has really set in.

In December 2010, several feet of snow fell in some sections of northern Europe that normally get only a few inches all year. Several cities in Germany shivered through coldest-ever temperatures sometimes reaching —20 degrees Celsius (—4 degrees F) In 2011, New York City posted its snowiest January on record, as the monthly snowfall total hit 36 inches (fl.4 cm). The normal snowfall in the city for an entire year is 22.4 inches (56.9 cm). Many people interpreted the cold and snow as evidence that Earth’s climate could not possibly be getting warmer.

A LOGICAL PROBLEM

Two opposite conclusions were drawn, each with evidence that was recent and easily observed by millions of people. Was Earth’s climate getting warmer or not? Which conclusion was right? Actually, neither. The unusual heat and cold observed in 2010 and 2011 are striking, but by themselves they indicate nothing about long-term processes such as global warming. The logic is faulty because it treats two separate phenomena, weather and climate, as if they were the same thing.

Weather is what happens in the short term—day to day, week to week. It’s today’s rain or tomorrow’s sunshine or the strong wind that messes up your hair. Climate exhibits itself over much longer periods. Weather indicates climate, but only if observed long enough to tell a coherent tale. A weather pattern that occurs in 40 years out of 50 may start scientists suspecting’ a climate change. The scientists— or their grandchildren—would feel a lot more confident announcing climate change if the pattern held for 80 years out of 100. Of course, climate determines what weather is normal. Consider the “Bermuda High’ that establishes itself over the Atlantic Ocean each Summer.

This qualifies as a climate feature because there is long-standing evidence of it, and it influences the weather over a very large region for a very long time. A strong Bermuda High has many effects on weather. For one thing, it ensures that hot and humid air flows over the southeastern United States and even reaches more northerly cities like Washington, D.C. For another, a strong Bermuda High steers the energy of many July and August storms northward along the U.S. Atlantic coast instead of westward to the Gulf of Mexico. Meteorologists trying to guess where a hurricane may go are likely to check the strength of this climate feature before making predictions.

CLIMATE CHANGE AND HISTORY

Climate change can have huge effects. In ancient Rome, North Africa was known as “the granary of the empire, “providing much of the Romans’ wheat and other basic foods. Then, in about 100 BCE, the North African climate became far drier than in previous times, limiting farming to a few narrow strips beside the Mediterranean Sea. In northern Europe the interval from about 950 CE to 1250 CE, known as the Medieval Warm Period, altered civilizations. Ice in the North Atlantic Ocean melted enough to clear new sailing routes, and the Vikings of Denmark and Norway took advantage of the change.

They settled Iceland, established farm communities in southwest Greenland, and even sailed to what is now Canada. Then, in the late 1200s, northern Europe’s climate changed again, becoming much cooler. Vikings could no longer sail ice-free seas from Europe to assist their Greenland colony, which gradually died off. Iceland remained inhabited, but life was much harder than during the warm period.

Climatologists keep trying to develop a strategy for detecting climate changes without waiting a hundred years. They’ve run weather data through some of the world’s most powerful computers. Some of their models say that a warmer Earth would see greater extremes— hotter summers and colder winters and more vicious storms year-round. But when Cyprus broils or New York City gets buried in snow, is that an example of what the models predict?

No one really knows. The fact that all of the Earth’s ten hottest years on record have occurred since 1f98 easily reinforces the belief that Earth’s climate is warming. Then again, climatologists say that even this impressive statistic could just be a coincidence. Climate change is clearly visible only in hindsight, after it has already occurred.