Hurricane Katrina and Climate Change

This is the third of a series of Podcasts on the impact of Hurricane Katrina on the United States.

Hurricane Katrina, and Hurricane Rita which followed it, are some of the largest storms to hit the USA, and it appears that the increased frequency of very powerful hurricanes is linked to climate change, or global warming.  Dr Webster and his colleagues from the School of Earth and Atmospheric Sciences, Georgia Institute of Technology, in an article recently published in Science,[1] say that there has been a large increase in the number and proportion of very destructive hurricanes.  Since 1970 there has been a doubling in the proportion of storms in categories 4 and 5. In the North Atlantic Ocean Webster found an increasing trend in frequency and duration in the last ten years.  He concluded that the “global data indicate a 30-year trend toward more frequent and intense hurricanes … this trend is not inconsistent with recent climate model simulations that a doubling of CO₂ may increase the frequency of the most increase cyclones” although he thinks more work is required on the role of hurricanes in the general circulation of atmosphere and ocean.  Greg Holland of the NCAR was quoted in The New Scientist on the 15^th September 2005 says that the chances of this trend being natural, i.e. due to causes other than climate change, “are fairly remote.”  Kerry Emanuel of MIT also found a 50% increase in the destructive power of tropical storms in the last fifty years.

These hurricanes therefore give us one very powerful message, the effects of climate change are already with us, they are not something that will come in ten or twenty years, they are here today, and more worrying is the reality that things will now get worse, that the process of climate change is unstoppable in the short term, say of fifty years and that we have to now plan how we are going to live with it.  The situation will inevitably get worse, even if you stopped burning gasoline and all other fossil fuels tomorrow morning, because, as a recent National Center for Atmospheric Research[2] pointed out, the globally averaged surface air temperatures would rise about half a degree centigrade and global sea level would rise by another 11 centimetres (4”) just from thermal expansion alone by 2100, the report authors said, “we are committed to a significant amount of global warming and sea level rise because of the greenhouse gases we have already put into the atmosphere (Gerald Meehl).

Apart from increasing the destructiveness of storms global warming will have a number of impacts, because the increase in the temperature of the atmosphere affects the oceans and the atmosphere as systems, and these systems are the engines which produce our weather.  The precise effects of climate change on ocean currents and rainfall cannot be known, but what is now clear is that precipitation amounts will change, some areas will become drier and others wetter, and the amount of rain falling within a given period will change, heavier rainfalls increase the chance of flooding.  Warmer air temperatures will increase temperatures in some areas, but not equally in all areas, and will increase ocean temperatures (thought to be one of factors behind the increase in destructive power of hurricanes).  Higher temperatures will also cause the icecaps near the poles to melt, which in turn will increase sea level, and this could be the most destructive effect of all, the US Geological Survey has calculated that if all the ice sheets in the world melted that the potential rise in sea-level is over 80 meters (approx. 260 feet), and that a rise of only 10 meters (32 feet) would flood the land currently occupied by about 25% of the U.S. population, much of Florida would be under water, together with the Gulf coastal belt of Texas and Louisiana and large areas of the east coast.  The USGS notes that during previous interglacial period sea levels rose from 3 to 20 meters higher than current levels.  The USGS states that if our climate continues to warm then the volume of the ice sheets will decrease and that if the vulnerable West Antarctic ice sheet went that alone would result in a sea-level rise of about 8 meters.  Such large increases will not occur over a few years, but over centuries, but low-lying coastal areas, such as New Orleans and parts of Florida, the Netherlands and the East Coast of England, will experience problems even with the initial increases in water levels.  Low-lying islands such as the Bahamas, the Maldives and the Marshall Islands face an even greater threat as they could be inundated by a rise in sea level of only 3 to 4 meters. In September 2005 the NSIDC reported that the amount of sea ice on the Artic Ocean shank in the summer of 2005 to what is probably its smallest size in a century, this was attributed “at least in part” to global warming.  One of the scientists said that this makes it “pretty certain that a long-term decline is under way.”[3] 

The complexity of the planet’s ecosystem means that it is difficult to precisely model the effects of climate change, but it is now clear that global warming will increase air pressure, which itself is thought to be responsible for the recent droughts in Southern Europe and milder, wetter winters in Northern Europe.  Other parts of the system which may be affected are ocean currents, such as the Gulf Stream, which carries huge amounts of warm water to North West Europe, and the high altitude wind systems (the jet stream).  We have now entered on an experiment which is in danger of running out of control, producing results which we cannot anticipate. 

The Intergovernmental Panel on Climate Change (IPCC) predicted that the U.S. would experience more frequent extreme weather events as a result of global warming, an increased incidence of floods and stronger hurricanes.[4]  The IPCC warned generally about the likely increases in the spread of topical diseases (including malaria, cholera and dengue fever) as temperatures increase and in deaths linked to extreme temperatures, as has recently been seen in Arizona.  Agriculture, forestry and water suppliers can be adversely affected by higher temperatures and changing rainfall patterns.  Many food crops cannot grow properly in very high temperatures and increases in temperatures and loss of rainfall can create deserts.  Changes in wind systems could also have disastrous consequences for countries like India which rely on the Monsoons for much of their annual rainfall, the failure of the Monsoons would mean that India would be unable to feed itself.  China is also a fragile ecosystem and currently suffers from a lack of water in the north eastern provinces, both these huge population centers are viable to climate change.

The models on which much of the previous work is based projected an atmospheric temperature increase of between 1.4 C to 4.5 C, but recent research at Oxford University has suggested that the actual increase may be up to three times higher, in a range from 1.9 C to 11.5 C, this would have dramatic effects on the whole planetary system.[5]  A recent report called “Meeting the Climate Challenge” published in January 2005 said that “beyond the 2 C level, the risks to human societies and ecosystems grow significantly.”[6]

Climate change is no longer a possible future that we can avoid by driving smaller cars and turning down the heating. What we also have to do is work out how far we need to change our energy usage in order to stop the effects of climate change accelerating, and to what degree we can stabilize the new system.  Up to now most of us have been sleep-walking to disaster, Katrina and her sister hurricanes are a wake-up call, especially for Americans, who use a full 26% of all the Earth’s energy,[7] but who only comprise 4.5% of the world’s 6.5 billion population,[8] fives times their share of the world’s energy.  Burning gasoline is getting to be seen as being as dangerous to our health as smoking, except in this case the US is the heavy smoker on 80 full tar Marlboros a day, and Africa and Asia are the passive smokers suffering from the flumes blown their way by the US; the Humvee is the equivalent of the guy who blows his cigarette smoke in your face.  Expect a warning from the U.S. Sturgeon General on every gas pump, and European tax levels on gas to discourage its use.

Now the people who are telling us that things are changing are not a bunch of drug-using crazies living in tepees in Northern California, or disaffected professors with a political agenda, they are large and respected institutions including the United Nations, NASA, NCAR, the European Union, the USGS, and various bodies of the U.S. Government.

So wake up and smell the coffee, you can't afford to ignore this issue any longer, even if our governments are side-lining it, the disaster that hit New Orleans, the bodies in the streets, tell us that global warming is here and that it is the biggest threat that we face, far more important than terrorism, or oil supply, it is a threat to the survival of millions of people on this planet and to the industrial society we have created.

You can also listen to the Podcast of this Article.