Global warming 2

Continuing from yesterday

What is global warming - About half of the sun's energy reaches the earth's surface. The rest is either reflected back into space by the atmosphere or absorbed by gases and dust particles. The solar energy that does reach the earth's surface, warms the land and oceans. In turn, the land and oceans release heat in the form of infrared radiation. Greenhouse gases absorb some of this radiation, warming the lower atmosphere, acting like a blanket and keeping the planet warm enough to sustain life. Without this blanket of greenhouse gases, the earth would be in a permanent ice age - this is all fact.

What are greenhouse gases - apart from water, there are six main greenhouse gases, three occur naturally and three are manmade. The three naturally occurring gases are; carbon dioxide, methane and nitrous oxide. The three manmade gases are; hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride. By far the most controversial gas is carbon dioxide and is the only one I will be discussing.

Example of greenhouse gas - water vapor in the form of clouds makes a very effective greenhouse gas. Have you ever noticed that the coldest nights have clear skies. The reason why deserts are so hot in the day is that they are good reflectors of radiant energy. The heat in the desert is coming from below, not above. At night, with no insulating layer of greenhouse cloud, the temperature plummets.

What is the big deal with CO2 - from yesterday's text, for the last 2.5 million years, the earth has been cycling in and out of ice ages. At the temperature peaks, the carbon dioxide atmospheric levels have been measured at 280ppm and at the temperature lows (ice age) 180ppm - proven fact.

The current carbon dioxide level is around 400ppm, a very significant increase from where it should be, at 280ppm. This increase in the carbon dioxide greenhouse gas is causing the atmosphere to trap more heat and the climate temperature to rise - this is a fact that cannot be disputed.

All this extra carbon dioxide has been poured into the atmosphere by man in only the last 200 years. Since the start of the industrial revolution, our world has revolved around the fossil fuels of oil and coal, both of which are carbon based fuels, made from the forestry deposits of the carboniferous period when dinosaurs roamed the earth. We use them for heating, transport, energy creation, industrial processes, plastics and so on. Another significant source of carbon dioxide is the cement industry, were carbon dioxide is a huge by-product - all fact.

What is the effect now - for the last 1000 years, the temperature has been fairly constant with only minor ripples of variation. But, since 1900, the start of the industrial revolution, the average temperature has risen 1 - 2°C depending which report you read. This does not sound a very drastic rise in temperature, but any temperature rise is enough to increase the melting of the ice caps which will result in a rise of sea level - all fact.

There is a strong argument that the warming of the oceans is affecting weather patterns and is being tied in with the extraordinarily extreme weather of the last twenty years; droughts, floods, tornadoes etc. - conjecture, a strong argument, but not proven.

What is the effect in the future - The really scary thing is the carbon dioxide graph, it is pointing straight up. If nothing is done about the rate of increase of atmospheric carbon dioxide, then the temperature graph is going to follow suit. This will result in more melting of the ice caps and rising ocean levels - this is fact.

The warming ocean temperatures will lead to more extreme weather. The possibility exists of changing ocean currents, which will dramatically change weather patterns around the world. This is a really bad situation - but again, conjecture and not proven.

Past precedents - During the cretaceous period, 145 to 66 million years ago, the time of the dinosaurs, there is strong evidence that the earth's temperature was 10°C higher than it is now, with the carbon dioxide levels much higher than they are now, although I cannot find exact numbers.

Mammals had started to evolve around this time although they did not really get going beyond mouse size until after the mass extinction at 66 million years ago. After that, the paleogene period, the real time of mammal diversification, possessed an atmosphere with 500ppm carbon dioxide average and an atmospheric temperature of 4°C higher than today.

Clearly, man is not in any immediate danger of extinction, but at the rate of carbon dioxide emissions, we are heading for paleogene temperatures by the end of this century and Jurassic park temperatures in a few hundred more. Temperature changes of such significance normally happen over time periods measured in millions of years, NOT hundreds. Such a rapid temperature rise is not going to allow man or any other life forms, time to evolve and adapt. There will be extinctions, but man will survive, we will simply design clothing to cope.

What can be done - because carbon dioxide stays in the atmosphere for a hundred or more years, the best we can do is to stop emissions as soon as possible and live with the damage that has already been done.

If we stop all emissions now, then we stop the temperature from rising further. Simply reducing emissions is not going to solve anything, but it will at least buy us a little more time by slowing down the effects. This would give our scientists more time to evaluate the dangers and our engineers to come up with solutions.

Can carbon dioxide be reduced - yes it can. New plant growth does absorb carbon dioxide and this needs to be done as part of a recovery strategy. BUT, this is not a solution to the present day situation. Plant absorption cannot cancel out what we are pumping into the atmosphere right now. Plant absorption is a long term climate control tool for the future.

How long have we got - if we want to stop the planet's climate from getting warmer, then we are out of time. We are already in damage control territory. The dam is already starting to crack. Simply reducing the size of the hole is not going to stop anything.

The question is how bad do you think the damage is and how much worse do you think it will get. Keep in mind that without a significant reduction in emissions, the carbon dioxide levels are likely to reach 500ppm by the end of the century, possibly even higher. You need to decide how bad do you think this will be.

Is it all a myth - The part about the temperature rising is all fact, as is the melting of the ice caps. The changing weather patterns, as far as I know, is not proven, but a very reasonable and compelling argument. If the weather connection is proven beyond doubt, then we could be in for some rough times ahead.

Today has been all about presenting the evidence, not to try to make up your mind for you. I have done my best to separate what is proven and what is conjecture. I guess it all comes down to the deteriorating weather argument. 'For or against', that is your decision. Why not tell me what YOU think.

Tomorrow I will finish off by presenting my thoughts on the subject - to be continued.

Dave