Climate Change Will Cause Extreme Weather to Worsen
Lord Hunt of Chesterton, Vice-President of GLOBE International and the former Director General of the Met Office, looks at how climate change will effect the weather and lead to more and more extreme conditions across the globe.
What should politicians, governments and the general public make of the ‘climate sceptics’ cry that ‘global warming has stopped,’ even though their position is based on a misleading interpretation of trends in the yearly average surface temperatures over the past ten years?
Climate scientists and decision makers around the world need to address this controversy, although they are generally more interested in understanding the connections between global trends and the patterns of record breaking extreme weather that are occurring everywhere. Even the sceptic bloggers admit to the seriousness of certain trends such as the steady increase in peak rainfall rates that is happening everywhere; it has doubled in South East Asia.
Not only global surface temperatures, but many other past and present measurements in the atmosphere and oceans, together with the results of climate models, help to explain how the climate is changing. Although there are uncertainties, especially in the timing and magnitude of climate variability, research does indicate what kinds of climate variations are expected over the coming decades, both through the natural unsteady dynamics of the climate system and from warming produced by the steady rise of greenhouse gas emissions. Explanations are better if relevant data and research results are not overlooked, which can result from the over rigid emphasis by international bodies of using results that only appear in mainstream English language journals. Equally, as new aspects of climatic processes are identified, research efforts need to be redirected, for example as to how atmospheric warming is now stimulating the natural production of greenhouse gases in the Arctic.
The controversy about recent trends in average surface temperature over the globe is, in my view, partly resolved by noting how the average surface temperatures of the oceans have been decreasing over the past decade. This is occurring not only in Arctic waters where the ice is melting, but equally strongly in the eastern Pacific, where winds off the South American coast cause upwelling and bring deep waters up to the surface. Normally this ‘La Nina’ phenomena lasts only a few years; its continuation for over a decade is partly caused by the easterly trade winds along the equator that are strengthened by the general warming of the atmosphere in this region. This also drives the East-West Walker circulation in the atmosphere. At the end of this phase in these regular oscillations, the surface cooling eventually ceases, and then, as has occurred on many previous occasions, there will be a substantial warming of the ocean surface layer around large areas of the globe. There will probably be damage to agriculture and fisheries in many countries, resulting in rising food prices (as the meteorologically knowledgeable British Prime Minister Mr Heath explained to the House of Commons in 1973 after a previous El Nino).
A further cause of concern is that the increase in ocean currents in the equatorial pacific is raising the sea level 2 to 3 times faster than the rest of the globe. Politicians in the Micronesian islands fear that the penetration of salt water into the atolls will destroy first the vegetation and then, before the end of this century, life on these islands.
During the last decade the average surface temperature over the land areas of the world has steadily increased (according to the US institutions which differ slightly from the UK studies in how the polar regions data are accounted for). This vital fact is not known to many decision makers who are only presented with graphs in which the ocean and land temperature data are combined. The chairman of the UK Environment Agency has recently pointed to more flooding as a consequence of how climate change is impacting on atmospheric processes. There is greater vertical mixing in the atmosphere; cumulus clouds are becoming stronger and higher, rainfall intensity has risen to dangerous levels, high mountains are losing their snow. Lightning and thunderstorms occur where they never happened before, as the Met Office global lightning system and my friend in Yellow Knife can confirm. Russian politicians have certainly moved from a position of scepticism to one of real concern as they experience the melting of the perma frost in the far north and the possibility of further prolonged heat waves and droughts. Mr Gorbachev emphasised the likelihood of more events like the burning forests around Moscow in 2010. Australia has seen the same trend. Winter cold periods will also be extended.
For the UK it was expected that there would be more extreme rain events and more droughts and heat waves, which even led some optimistic landowners to start planting olives on the Scottish borders. But the big surprise has been the spells of colder winter weather, even though earlier projections of the Gulf Stream ‘turning off’ had already been abandoned. The Met Office (which was founded in part to study the Gulf stream in 1854) has shown, based on its climate models, that the westerly Atlantic winds provide about 50 or 60% of the driving force, which is consistent with recent paleo studies of its historic variability. However if a large part of the arctic ice melts, as now happens every summer, the winds over the ice-free ocean can push much of the current up to Iceland and the Arctic ocean. As a result colder waters from the North, and northern UK may no longer receive the same level of warming as it did when the ice was there. Detailed research using the Cryosat satellite measurements of the ocean level and climate computer models is showing how these ocean currents are changing, and there are interactions with the high level atmospheric jet stream as it steers the winter weather over Europe.
Responsible nations of the world are now preparing for the effects of global warming, especially extremes in weather and unprecedented variations in behaviour of the oceans and ice. Governments need encouraging to maintain and expand national and international programmes to reduce greenhouse gas emissions, since, as the Stern report concluded, adaptation policies to reduce the impacts of climate change will then in the long term be more effective and less costly.
Lord Hunt of Chesterton is Vice-President of GLOBE International and the former Director General of the Met Office