Global Warming Explained
Global warming has come about from human beings becoming more technologically advanced. It started with deforestation to build cities, ships and other wooden items, burning coal to keep warm during long cold winters and then, in the 1800’s the start of the industrial revolution meant that we started burning the three main sources of greenhouse gases: oil, coal and natural gas (methane) without any thought to the negative effect this ever increasing activity would have on our biosphere.
The Greenhouse Effect
Carbon dioxide (CO2) and methane (CH4) exist naturally in the atmosphere and have a great ability to trap energy (heat) longwave terrestrial radiation going out from the earth. The sun’s energy comes into the earth in the form of shortwave solar radiation of which only 25% is reflected back into space by the atmosphere. Of the other 75% only 3% is reflected from the ground back into space. The rest is absorbed by the ground, ocean and atmosphere. As the earth’s surface heats it re-emits this energy (heat) back out in the form of long wave terrestrial radiation back into the atmosphere. This would escape into space if it wasn’t for carbon dioxide and methane’s great ability to trap longwave terrestrial radiation going out to space. So it’s like a one way window: the shortwave radiation energy (heat)from the sun is let in and and the longwave radiation energy (heat)from the earth is trapped going out. This greatly reduces the amount of energy (heat) that escapes back into space, therefore the planet warms up. The greenhouse effect.
Yin and Yang
Before the industrial revolution CO2 was a good thing because it kept the earth’s atmosphere at a temperature suitable for life to exist. The earth was in balance, and tended to soak up the carbon dioxide it emitted. If there was no CO2 or methane in the atmosphere the earth would be about minus 18ºC. The earth would be mainly ice and very little life would exist.
The Greenhouse Gases (GHGs)
The greenhouse gases listed below are only 1% of the total gases that make up the atmosphere that we live in. These tiny amounts of gas are what scientists call trace gases and are measured in PARTS PER MILLION. These tiny amounts of gas can have a devastating affect on the earths climate systems. Here is a breakdown of the 1%.
CFCs’(chlorofluorocarbons) make up 6%, lasts for 200 years and is 15,000 times more effective at trapping out going long wave radiation than carbon dioxide. 11% is made up of Nitrous oxide, Ozone and Halocarbons. Methane (CH4) lasts for 12 years in the atmosphere and makes up 19% of the greenhouse gases in the atmosphere and is 24 times more effective at trapping longwave terrestrial radiation than carbon dioxide. Carbon Dioxide makes up 64% of the greenhouse gases in the atmosphere and that is what we pollute the atmosphere with the most. It lasts in the atmosphere over 100 years. The heating effect from CO2 and other gases hangs around in the troposphere and close to the ground. It is only 11Kms from the ground to the top of the troposphere.(This is called the tropopause where the troposphere mets the stratosphere).This has a double whammy effect because the warmer air has expanded and is now able to soak up more water vapour more readily by evaporation from rivers, lakes and the ocean. The new water in the atmosphere acts as a greenhouse gas in its own right by holding the heat in the air, in the form of water vapour and doubling the effect of the greenhouse gases. Water vapour is the biggest greenhouse gas by far, because the energy that was used to make the water go through a change of state from water to vapour (Sensible and Latent Heat), that energy is now helded in the atmosphere in the form of water vapour. (The more water vapour, the more energy held in the atmosphere hence the increase in earths temperature). This warmer air melts the ice and snow on the North and South Pole, The Mountain Ice and The Glaciers.
Feedback effect
Ice and snow reflect 90% of the sunlight (shortwave radation) back into space. With the increase of temperature caused by more CO2 in the atmosphere ice and snow are tending to melt. Especially at the poles. The land and sea once covered by ice now absorbs the sunlight which causing further temperature increase. The warmer surface of the ocatureean also helps to melt the North and South Poles further. This amplification of the increase of temperature is known as a positive feedback effect. (“Positive” in this context refers to the amplification of the effect, it does not mean it’s good.)
More unpredictable weather events
The extra water vapour in the air and the warmer ocean surface temperature leads to more unpredictable weather events like flood, drought and cyclones.
Ocean currents at risk
The top 100 metres of the ocean’s water is warmer and a difference density to the colder waters below. This is called stratification and is how the oceans water currents work. The top 100 metres is warm and heavy with salt due to evaporation. The ocean currents carry it to the north and south poles where the ice cools the salt-heavy water which then sinks to the bottom of the ocean which in turn drives the worlds’ ocean currents (in a nut shell).
The risk is when the North Pole disappears altogether in the next 15-20 years or sooner, what will cool the ocean surface current and drive the deeper ocean currents? If the oceans currents stop, humans will never be able to restart them and weather patterns will change around the world. Scientists now have a pretty accurate record of the earths’ temperature and carbon levels going back 650,000 years through ice core samples, tree rings and drilling core samples out of coral. They are able to say that carbon levels in the atmosphere go hand in hand with the earth’s average temperature.
Can it be proved!
Obvious signs are already in place including glaciers melting, little or no sea ice for the first time in recorded history, North Pole melting, massive chunks ice breaking off in the South Pole, more hot years, longer droughts, bigger and more violent storms every year and altogether strange weather patterns that you see yourselves in everyday life.
The stratosphere just above the tropopause should be warmer than what it is now from the outgoing long wave radiation. However this is not the case. The outgoing long wave radiation is being trapped by the increase in carbon dioxide and other gases, which causes cooling of the lower part of the stratosphere.
Satellites and weather balloons measuring equipment have recorded that the lower stratosphere has cooled by 0.3% to 0.6% per decade since 1980 which is what is expected if greenhouse gases were trapping out going long wave terrestrial radiation in the troposphere. This is one piece of the evidence that the rise in earth’s temperature is man-made by carbon dioxide emissions and other gases.
It's Getting Hot
Since 1850 good records have been kept on temperature. In the last 160 years the hottest years on record have been: (in order)
1st. 1998
2nd. 2005
3rd. 2002
4th. 2003 (when 35000 Europeans died in the heatwave) and
5th. 2004
13 of the past 15 years have been in the top 12 on record.
The heatwave of 2003 caused the lowest harvest of wheat in the Ukraine for 30 years. The wheat harvest was down by 75% on the previous year.
450ppm of carbon dioxide in the atmosphere represents a 2.1°C change in average earth temperature which will happen in about 2024 - 25 at the current levels of increase.
Everything is interdependent
What we need to understand is that all life on earth exists through a series of interconnected ecosystems on which all life depends (including human life). When one is affected, then so is another and another, like a set of dominos falling in a line. We are fast heading to destroying two major ecosystems which absorb 80% of the earth’s carbon dioxide. They are the ocean algae and the forests.
What will happen:
- More heatwaves, forest fires and longer droughts
- The collapse of coral reef and fishery ecosystems
- Migration of millions of people to find food and water
- Ocean currents weakening and changing weather patterns
- Some Pacific Islands become uninhabitable due to rise in sea level
- More powerful storms and floods - affecting 2 billion people
- Wheat and rice crops will fail due to higher temperatures - this will affect 2 billion people
