(This is Part 24 of a series. Go back to Part 23.)
The final secondary effect of industrialism, now showing up more and more strongly, is climate change.
As sunlight strikes the earth, some of it reflects back up to the atmosphere. CO2 molecules in the atmosphere absorb this energy and radiate some of it back to the ground, thus contributing to the warming of the earth—a phenomenon known as the greenhouse effect.
The stable levels of CO2 in the atmosphere for the last 20 million years or so have helped to keep the earth within a fairly narrow temperature range during that time, greatly facilitating life. However, as discussed previously, that is now changing and carbon dioxide levels are rising rapidly as the prodigious burning of fossil fuels continues.
With these rising CO2 levels have come an increase in the greenhouse effect and thus rising worldwide temperatures. The average temperature of the earth has risen about two degrees F. during the 20th century and is projected to rise another three to ten degrees F. in the 21st. Doesn't sound like all that much, does it? What's the fuss?
Here's why it is far more significant than it may appear:
First, we might want to note that the difference in average temperature between the present time and the Ice Ages is only 9 degrees F. In other words, just a slight difference in average temperature can mean massive changes in our earthly environment.
Second, let's remember that this rise in global temperature is an average. Temperatures are rising much more over land than over the oceans; they are rising much more in northern latitudes than at the equator; and they are rising much more inland than at the coasts.
Put all that together and what we get is that temperatures are rising much more in inland areas at northern latitudes —the breadbasket areas of the earth.
Now let's look at plants for a moment. All human life, of course, ultimately rests upon the bedrock of agriculture. And agriculture in turn depends upon a little thing that plants do called photosynthesis, which converts sunlight into stored chemical energy—food. In the simplest terms, without photosynthesis we all die.
Many of the agricultural areas of the earth are suffering from heat stress already as temperatures climb into the 90s during the growing season. Why does that matter? Because as temperatures rise, photosynthesis declines.
And photosynthesis stops completely at 104 degrees F.
At 104 F. a plant is in heat shock, just trying to survive.
Thus the continuation of global warming will have grave implications for agriculture. At the temperatures projected in this century farmers will be trying to grow crops in an environment which is unprecedented in the 11,000 years since agriculture began.
(This is the end of Part 24. Go to Part 25.)
—jim sloman, 10.21.04 for Sep 13
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