The National Climate Assessment was recently released and it focused on Global Warming and its short and long-term effects. This column isn’t intended to change anyone’s mind either way on the subject but to provide some information and hopefully make it easier to shift through all the dross out there.
The most important thing to understand is the difference between climate, weather, and what the “Global” climate is. First some simple definitions are in order.
• Climate - The weather conditions prevailing in an area over a long period of time.
• Weather - The state of the atmosphere at a given location and particular time including such factors as air temperature, wind, humidity, cloudiness, precipitation, and so on.
• Global climate - Global climate is the average climate over the entire planet.
In the most basic terms “Climate is what you expect and weather is what you get.” And while we tend to think of climate and weather as it relates to where we live, the planet as a whole has a “climate” – a set of average atmospheric conditions. Those are adequate definitions but they don’t explain why we have weather and climate and that understanding is really the key to the whole issue.
Nature has two inviolate rules. First, everything must move from a higher to a lower energy state or from more to less, and things seek the lowest energy state possible. Second, nature loves equilibrium and prefers there not be any differences. So where differences in energy, pressure, or concentration exist, a gradient is formed and everything flows downhill. Our planet receives its energy from the sun as electromagnetic radiation. Some is visible to us and some isn’t. Some is reflected back into space as it reaches our atmosphere while some is absorbed by the atmosphere, oceans, soil, etc. Some of that radiation is radiated back into space as invisible longwave (infrared) radiation. That alone doesn’t create weather (wind, storms, etc.) the tilt of the Earth’s axis does. Because the earth is tilted at 23.5 degrees there are a variety of effects we wouldn’t experience if it weren’t.
• As you move from the equator to the poles day length varies between seasons.
• Differential heating occurs resulting in large temperature differences seasonally as you move away from the equator to the poles.
• These temperature differences result in air pressure differences.
The atmosphere tries to eliminate these differences by having high pressure move to low and warm temperatures to cold. Add to all this the properties of the atmosphere and how it holds heat. Some components of the atmosphere let radiation pass through easily such as nitrogen. Some absorb heat (Carbon Dioxide, water vapor) as it leaves the surface while letting visible radiation in and hold this heat and/or reradiate it back towards the earth. The more of these compounds present in the atmosphere the more the heating of the Earth and its atmosphere. This raises not only air temperatures but pumps more energy into the climate cycle. This results not only in different weather but a different climate. Next week’s column will explore this possible change.
Dr. Victor L. Martin is the agriculture instructor/coordinator for Barton Community College. He can be reached at 620-792-9207, ext. 207.