Feature Article April 10, 2003
LAND O' LAKES NewsWeb HomeThe climate is warming-how can they say that?by Gray Merriam Clearly we have had an unusually cold winter around here, and yet we are told there is global warming. How can we have such a paradox? Some think its just a scam.
Not necessarily. How can we tell if the "climate is warming"? First we must recognize that temperatures vary -- a lot. Both over time, day to night, July to January, and also geographically -- across space. So what temperature are we talking about? August highs or January lows? And where? Baffin Island, Ottawa, Miami, over the mid-Pacific? Once we think about variation, we can ask: Is it possible to have global warming and, at the same time, have a record cold winter around the Great Lakes?
The answer is yes. We can find many different temperatures, both cold and warm, across the earth's surface and, over a longer time, the average temperature may be rising a little but some spots may be unusually cold for a shorter time. A scientist might say "both the mean and the variance are increasing".
Trying to actually measure all the earth's temperatures -- day and night, summer and winter, in the arctic and in the tropics, over land and at sea -- and check whether the average has changed 0.5 degree C does not seem like a very satisfactory way to find out whether 'the climate is warming'.
What are some other ways? Wild species and their habitats sense climate constantly and reflect any changes in where they can live and how well. Take one example - the Polar Bear. When there is sea ice, they roam widely over it hunting seals. In the off-season they are restricted to the tundra shore. They must live off stored fat. They cannot hunt without the ice. When trapped on shore they have to protect themselves from the heat of the arctic summer. They are so well adapted to the cold of the winter sea ice that anything else is difficult for them. They really are ice bears.
Recent records and observations by people who live there show that arctic sea ice is freezing later and melting sooner than in the past. Polar bears are forced to stay on land longer each year. They can hunt and feed less. This extended ice-free period is already reflected in the body condition of the bears. The weight of Hudson's Bay bears has declined significantly over the last several years and that is causing lower survival of cubs. Biologists are already concerned that changing conditions could lead to a severe decline in polar bear populations.
How many other examples can you think of where environments are changing and species are shifting their geographic range in response? Are there any invasions by exotic species formerly restricted to warmer climes? Look on the larger scales -- regional, national, continental. Don't fall prey to the trap of looking just out your window when trying to answer global questions like 'is the climate warming?'
