The debate on global warming – skeptics and believers

Introduction

The earth receives solar energy in the form of heat and light. Some of this energy reaches and is absorbed by the earth’s surface. Much of this absorbed energy is re-radiated back into space. However, if most of this energy is re-radiated back into space most life on earth would perish, since the surface temperature would drop significantly making the earth much cooler.

This is where greenhouse gases come into the picture. Greenhouse gases (water vapor, carbon dioxide, methane, nitrous oxide, ozone and chlorofluorocarbons) absorb this re-radiated energy thereby keeping the heat trapped in the atmosphere. So far, so good.

An increase in the concentration of these greenhouse gases, however, would result in more heat being trapped, which would in turn cause rising temperatures on the earth’s surface.

Enter global warming

With the industrial revolution the world has seen rising emissions of greenhouse gases (especially CO2). Climate scientists argue that this anthropogenic increase in the concentration of greenhouse gases is causing rising temperatures on the surface of the planet. If left uncontrolled, it could lead to disastrous consequences.

So, is it a real threat?

In spite of mounting evidence towards the threat posed by global warming, there are many skeptics (including eminent scientists such as Freeman Dyson) who vociferously dismiss global warming as nothing but hype.

The arguments from the skeptics can be broadly grouped into three categories:

1) Global warming is not manmade

Skeptics – Global warming is a natural phenomenon. Human CO2 emissions account only for a fraction of the total CO2 emissions. Changes in the composition of greenhouse gases and other atmospheric effects are very difficult to estimate and climate models are often fraught with uncertainties [5]. Further, solar activity might be influencing the weather causing warming.

Believers – Over the last ten thousand years the atmospheric CO2 levels were stable at around 275 ppm. However, just in the last two hundred and fifty years the levels have risen to around 350 - 375 ppm [6, 7]. Humans emit twenty six Gigatonnes of CO2 per year [6].

Climate models might not be 100% accurate. However, there have been lots of models run by independent groups and none of these models are able to predict the recent warming without taking rising CO2 levels into account [8].

As for solar activity, the sun definitely plays a role in climate change. However, there have been studies that establish that the role of the sun is minor - "+/- 1% for the 20th century and negligible for warming since 1980" [4, 5].

2) Global warming is not occurring

Skeptics – The global temperatures are no longer rising and seem to have plateaued. In fact, we have had global cooling over the last decade.

Believers – This seems to stem from the observation that 1998 was the warmest year in the last decade. Long term trends show that the surface temperature is steadily increasing [1]. Furthermore, studies show that over the last hundred years the mean sea level has been rising at a rate much higher than the rate averaged over the last thousand years [2].

3) Global warming is not necessarily a bad thing

The argument – Rising temperatures are not a thing to be worried about. This will give rise to an explosion in flora and fauna in parts of the world that are currently uninhabitable (such as Siberia and the ice sheets in Greenland) [3]

My subjective take (just on this point) – the world has man-made borders. People who have lost their land due to rising sea levels cannot pack up and relocate elsewhere. Unless people from Tuvalu will be moved to Siberia or Greenland once it warms up a tad bit more this argument does not hold water.

Summary

Global warming is a legitimate threat. More research needs to be done to better analyze the causes of warming and address the questions from skeptics. More importantly, while jumping into the fight against global warming we need to ensure that we do not divert attention or resources from combating other equal, if not greater, problems such as air and soil pollution. Irrespective of whether we believe in global warming or not, it would be in our best interests to treat the planet with more respect. Apologies if that sounded preachy.

References

1. http://www.ncdc.noaa.gov/oa/climate/globalwarming.html#q3
2. http://www.ncdc.noaa.gov/oa/climate/globalwarming.html#q9
3. http://news.nationalgeographic.com/news/2007/10/071017-greenland-warming.html
4. Benestad, R. E., and G. A. Schmidt (2009), Solar trends and global warming, J. Geophys. Res., 114, D14101
5. http://www.canada.com/nationalpost/news/story.html?id=985641c9-8594-43c2-802d-947d65555e8e
6. http://www.skepticalscience.com/Are-humans-too-insignificant-to-affect-global-climate.htm
7. http://cdiac.ornl.gov/trends/co2/lawdome.html
8. http://www.ipcc.ch/ipccreports/tar/wg1/pdf/TAR-12.PDF (see graph on page 703)