Global warming is a small increase in atmospheric temperature, of the order of 1 degree Fahrenheit per century. Because it is so small compared with the large daily and seasonal temperature changes, some writers have challenged its authenticity. Most agree, however, that the last decade of the twentieth century was the hottest on record, and all the global ice caps are melting. Therefore we can assume that global warming is real, and move on to questions about its causes, its impacts and what we can do about it.
Some of the most popular questions include:
- How do we know global warming is really happening?
- How do we know what the causes of global warming are?
- What are the potential impacts of global warming, and which of them are likely to affect us?
The first question is already answered by means of the evidence that the global temperature is rising although some might argue about the methodology in obtaining the global average temperature. One student I recall asked me if they had a thermometer in every square mile of the earth. Obviously we do not have that, but the folks at National Oceanic and Atmospheric Administration (NOAA) do a great job of monitoring the earth’s temperature. Check out the NOAA National Climatic Data Center for more details on how it’s done. We may also examine some of the effects that are attributable to global warming. These include the melting of the polar ice caps, recent super-storms Sandy and earlier Katrina. This leads us into the second question: what are the causes of global warming?
There are two rival theories on the causes of global warming. The first is the greenhouse effect, while the second is natural cycles. The former simply makes the case for greenhouse gases trapping heat on the earth’s surface by allowing solar radiation in while absorbing the radiation as it goes back out.
- Carbon dioxide- CO2
- Water vapor -H2O,
- Methane -CH4, a major component of natural gas and also of flatulent emissions from animals
- Nitrous oxide -N2O also called laughing gas (no joke)
- Chlorofluorocarbons – CFCs used in refrigerants and aerosol propellants
The greenhouse effect has always been present and is critical to our global temperature regulation but it is thought that an imbalance in the major greenhouse gas Carbon dioxide- CO2 is offsetting this balance. Steady increases in CO2 concentrations over the last century have resulted in a small enhancement of the effect. Other greenhouse gases also show significant increases, but the main contributor is CO2, associated with the burning of fossil fuels. Evidence from the ice cores show an increase in average CO2 concentrations from the last 1,000 year levels.
The other rival theory is natural cycles and is based on the idea that global warming is a natural phenomenon that has little to do with human activities. The Milankovitch explanation remains the most plausible and suggest that there are resonance in the sun-earth coupling. For a deeper yet simplified explanation read the Milankovitch Cycle. The premise from this theory is that global warming is due to the fact we are still emerging from the last ice age, which took place about 20,000 years ago. There is reliable evidence to support large sea level fluctuation, up to 300 m above and 200 m below current levels. Assuming this was the case then global warming is a natural phenomenon that has nothing to do with burning fossil fuels.
Irrespective of the theories trying to link the causes, we still have to deal with the effects and this brings us to the third question: What are the potential impacts of global warming, and which of them are likely to affect us?
The FDR Drive, flooded by Hurricane Sandy the evening of October 29, 2012 : Buzzfeed
The evidence is quite remarkable as the impacts become more apparent: Rise in sea levels due to (a) melting of polar ice caps, and (b) thermal expansion of the sea, flooding of low-lying territories, affecting corals, increased desertification, changing of weather patterns, perhaps even the frequency and intensity of hurricanes (Katrina, Sandy). At the planetary level we may be triggering a runaway increase in CO2,leading to the end of life on the planet. Note that our planetary neighbors, Mars and Venus, both have atmospheres with more than 80% carbon dioxide. Is this the end result of global warming?
Well, as the old adage says, better safe than sorry. Which theory do you suggest is more accurate and what mitigation strategies are more appropriate for it?