A study published on Sunday 2nd December in the journal Nature Geoscience is warning that the tropical belt around the centre of the Earth (the equatorial region) is expanding both northwards and southwards at an alarming rate. The pace of expansion far exceeds any of the current climate change computer models, which had predicted this type of movement towards the north and south poles nearer the end of the century. The study was carried out by a team led by Dian Seidel of the US National Oceanic and Atmospheric Administration in Washington. Other members of the team were taken from the National Centre for Atmospheric Research in Boulder, Colorado, the university of Washington in Seattle, and the university of Utah in Salt Lake City.

The report states that since 1980, the region around the equator classified as climatologically tropical has grown pole-wards by around 172 miles (276km), which means an additional 8.5 million sq miles (22 million sq km) of the Earth are now experiencing a tropical climate. Even the Intergovernmental Panel on Climate Change (IPCC) in their worst-case scenario did not predict this much expansion in the next 100 years. Dr Seidel said:

We are seeing indications that a warming climate is associated with expansion of the tropical region towards the poles, and the rate of expansion that has occurred in recent decades is greater than projected by climate models to occur in the 21st century… Remarkably, the tropics appear to have already expanded – during only the last few decades of the 20th century – by at least the same margins as models predict for this century. – The Independent

The report warned of the implications to the millions of people within the dry, sub-tropical areas close to the growing tropical belt. Changes to rainfall patterns and wind directions could cause these areas to become even more arid, creating the conditions for crop failure and famine. Dr Seidel said: “Shifts in precipitation patterns would have obvious implications for agriculture and water resources and could present serious hardships in marginal areas.” As the tropical area expands, so too will the areas affected by “tropical pathogens and their insect vectors” said Professor Barry Brook of the University of Adelaide.

Another, perhaps more alarming aspect of the report, is the prospect of irreversible climate change. The report explains that the expansion of the tropical belt could feed global warming by increasing the rate at which water vapour is pumped naturally into the upper atmosphere – water vapour is a greenhouse gas.

The pole-ward movement of the tropics is just another example of the effects of human-induced climate change. The consequences of climate change are yet to be fully understood or even appreciated. The experience of climate change is something we will all one day have to live with. All the indications are that day is not as far into the future as our political leaders would like us to think. Action is needed now, and it is needed on a global scale. Hopefully, the representatives from the 191 countries meeting on the island of Bali in Indonesia, to negotiate a new international treaty to cut down on greenhouse gas emissions, will actually take the issue seriously and commit to cut emissions. The pointless meetings in the past where politicians talked ‘green’ and effectively did nothing are a distraction and achieve little other than to create a media opportunity for those taking part. The only way politicians and industrialists will ever take action is through voter and consumer pressure. It is up to us to make informed choices with our votes and our money. We can help to reduce the human impact on climate change by making changes ourselves in our own lives, and by using our votes and our money to force change on a wider scale.