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Climate Change

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1 Climate Change on Sun Aug 05, 2012 9:34 am

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Climate change is the biggest and most controversial environmental issue of our times. Or rather, the cause of climate change is.

The fact that the Earth's climate has changed over its history - sometimes with cataclysmic consequences, called mass extinctions, for many of the planet's inhabitants - is not disputed. However, what has been the cause of fierce debate is whether or not human activity is currently causing a warming of the world.

What climate change, man-made or not, is not - is short term weather. These trends are much bigger and much longer term than a hot summer or a cold winter, we're thinking more of ice ages than cold snaps when we talk about climate change.

There are a number of reasons why the Earth's climate has changed historically. As the continents have moved through the process of plate tectonics they see changes in their climate, both as a result of the influence of the changing oceans and the size of landmass.

The Sun also plays a role: as the main source of heat and light for the planet, its activity is a major player in our climate and it is not a constant; fluctuating both cyclically and as it goes through its lifespan as a star.

The Earth's position relative to the sun is also not as constant as you might like to think, we're not in a circular orbit and the tilt of the planet also changes, causing changes in how all that heat and light from the Sun hits the planet's surface. Volcanic activity too can change climate by putting large amounts of material into the Earth's atmosphere and thus reflecting heat away from the surface.

Such large eruptions are however rare, in fact, the phrase ''once in a blue moon'' probably comes from the change in the atmosphere caused by ash plumes from the eruption of Krakatoa in 1883. It's also been theorised that asteroid strikes on the planet have a similar effect, throwing material into the sky, and some scientists believe that the end of the age of the dinosaurs may have been caused by a giant asteroid hit.

The final reason why climates change - and this is where the controversy comes in - relates to human activity, or anthropogenic global warming, which is what is meant when you read a news story about climate change.


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Primarily, this has referred to the misleadingly named greenhouse effect. While a greenhouse warms the air by allowing in and retaining heat and not allowing in cooling air, greenhouse gases warm the planet by absorbing the Sun's heat and then reemitting it into the atmosphere.

The main greenhouse gases are: water vapour, carbon dioxide (CO2), methane, water vapour, ozone, nitrous oxide and CFC-12, a chlorofluorocarbon the use of which in many countries as an aerosol propellant and refrigerant has been banned. With the exception of CFC-12, which is man-made, these gases have historically existed in the atmosphere and there have been natural fluctuations (for example volcanoes emit CO2) in their levels.

The most common of these gases and thought to be the most significant greenhouse gas is water vapour but it's one on which human activity has little effect. As air warms it can hold more water, the increase in water vapour is said to be responsible for a possible amplification of global warming as the temperature warms.

Plants, which rely on CO2 to survive and which use and store it as they photosynthesise are said to be natural carbon sinks and over history natural variations in the levels of CO2 in the atmosphere are thought to have been balanced by their action.


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However, since around the middle of the 18th Century, human activity affecting the levels of carbon dioxide in the atmosphere has rapidly increased. Since the industrial revolution took hold we not only burned more CO2-emitting fuels, from wood to coal to oil, but we have also massively reduced the amount of vegetation on the planet.

Is the Climate Changing

In July 2010 the British Government's Meteorological Office and the United States National Oceanic and Atmospheric Administration issued findings that they said showed unequivocally the world was warming. Using 10 indicators, seven temperature measures and three ice or snow cover measures, they said that each of the last three decades has been warmer than the last and successively broken temperature records.

Action on Climate Change

The reason why climate change has become so controversial is because people are being asked to make massive lifestyle changes in their lifestyle to help mitigate the effects of man made global warming. If action on climate change amounted to legislation to outlaw, say, wooden pencils then, while scientists may debate the rights and wrongs of the issue, you can almost be sure that our media would not be filled with the dispute.

The roots of world-wide action on climate change date back to the 1988 foundation of the Intergovernmental Panel on Climate Change (IPCC) by the World Meteorological Organisation, a department of the United Nations in 1988.

Since its foundation it has reported regularly on the state of climate change, with its 1990 report inspiring the United Nations Framework Convention on Climate Change (UNFCCC), the first international treaty that aimed to reduce global warming, which was signed at the so-called Earth Summit in Rio de Janeiro in 1992.

One of the key moments in the growth of concern about global warming was the release in 2006 of the film, An Inconvenient Truth. The documentary followed former US Vice President Al Gore as he tried to convince audiences about the seriousness of climate change. Gore won a Nobel peace prize as a result, but, like everything else to do with climate change the film has been the subject of much debate, particularly when schools have tried to show it to pupils.

The countries that signed the treaty have met since, with much fanfare, but often to little effect. The most recent major meeting was at Copenhagen in 2009 and was widely criticised by environmentalists.

Much of what has been agreed is also controversial, particularly so-called carbon trading arrangements which aim to set a marketplace for carbon credits sold by those who live with a small carbon footprint or contribute to carbon reduction by, for example, planting trees, to those who pollute.

Most countries have set targets for the reduction in carbon emissions. For example, the British Government's Climate Change Act of 2008 set legally-binding targets of a 34% reduction by 2020 and at least 80% by 2050.

Consequences

Again, the possible consequences of climate change are the subject of much to-ing and fro-ing with accusations of irresponsible scare-mongering and reprehensible complacency flying between the parties.

However, the IPCC has produced estimates - and the sheer complexity of climate systems and thus the difficulty of predicting how they will react using computer models makes them open to criticism - of what may happen as temperatures rise. Broadly speaking, most are catastrophic to both human life and to many other species on the planet.

Controversy

Unless you've already moved under a rock in preparation for climate chaos, you will have noticed that the issue of global warming is a controversial one.

There has been criticism of the IPCC and its work, the so-called climategate scandal involving leaked emails from the University of East Anglia's climate studies centre and doubt has been cast on the very idea that humans could be causing warming of the globe.

Even the controversy is controversial. Environmentalists often refer to climate sceptics as climate deniers, claimed by their opponents to be a deliberate attempt to ally them in the public mind with far right wing holocaust deniers. Many who criticise the science that claims to show that human activity is causing global warming are accused of being funded by the oil industry and free market think tanks who oppose the sort of government regulation that it seems will be necessary to implement large reductions in greenhouse gases, especially CO2

Personal Action

One of the strongest ideas of the green movement has been 'think global act local', which empowers people to believe that their own actions can have an effect on problems that are as big as the planet.

This applies to climate change arguably more than any other issue. What can I possibly do? Has even become a plaintive refrain of whole western nations shrugging their shoulders as they watch the rapid and dirty industrialisation of new economic giants like China and India.

However, once you accept the idea of climate change, then doing nothing doesn't really seem an option. It's possible to join any number of groups which campaign for environmental issues and almost all of which make global warming a major part of their efforts. Lobbying your elected representatives as an individual or as part of a group is your right as a voter.

The good news is that changing your lifestyle to reduce your carbon footprint might not just be cheap; it might even save you money, because broadly speaking, the less you consume, the less damage you are likely to do. You can, of course, speed a good deal of money on advice and carbon trading too.


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Reduce your car use and try and drive more fuel efficiently, if you can, buy a car powered by alternative, greener means. Try not to use products made from oil, looking for green and vegetable-based alternatives is a good idea. Cut down on your power use - while efforts are being made to introduce renewable energy (and you can opt to pay a little more to use them with some providers) to western societies, the vast majority of our heating, light and power comes from carbon emitting production methods

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Yesterday saw the release of the first UK government report on the possible effects of Climate Change upon the UK. Today the government has announced a 'National Adaptation Programme' to prepare the UK for climate change and its probable effects.

Following 24 hours of press releases, behind-the-scenes analysis and further comprehensive details being released by the UK CCRA (Climate Change Risk Assessment), we can now see the 100 foremost challenges the UK is likely to face. One of the purposes of the report is to ensure that "The UK is set to be amongst the best prepared nations for the implications of climate change"; the report is designed to be a baseline for government and local authorities to use in their planning and therefore doesn't take into account any future policies or actions that have been planned to combat climate change.

The response to the report, the National Adaptation Programme, includes the development of a new website where members of the public are invited to make suggestions. The report takes into account the possible economic and day-to-day impacts climate change may have, and people are encouraged to contribute their specific ideas concerning protecting their places of work.

Announcing the report, Environment Secretary Caroline Spelman said:

"This world class research provides the most comprehensive case yet on why we need to take action to adapt the UK and our economy to the impacts of climate change. It shows what life could be like if we stopped our preparations now, and the consequences such a decision would mean for our economic stability.

The Climate Change Risk Assessment will be vital in helping us to understand what we need to do to stop these threats becoming a reality. In doing so there is also great potential for growth through UK firms developing innovative products and services tailored to meet the global climate challenges."

Professor Sir Bob Watson, Chief Scientific Adviser at Defra, said:

"The CCRA is ground-breaking research which puts the UK at the forefront of understanding what the projected changes to our climate will really mean for us.

"For the first time it means we can compare a wide range of risks based on their financial, social and environmental implications. This will be invaluable for Government in prioritising the areas for future policies and investment, and it will help businesses assess what they need to do to ensure they are resilient to the changing climate."

The report outlines key areas for concern were the UK not to take any action to prepare for, and prevent, severe climate change. Of particular note were concerns over the health of elderly people and children with concerns over heat-waves and access to water topping the list. One of the predictions suggested there could be 580-5900 additional premature deaths per year due to hotter summers. With regards to water supply, The Thames River Basin and more surprisingly, Scotland are presented as major areas of concern, however Defra's Water White Paper including shortage supply measures (published last year) is not taken into account in the report.

Other concerns included flooding and increased temperatures, with extensive information on the potential economic costs, suggested adaptations to building cooling funds and suggestions for improved insurance processes. In contrast to flooding, drought is considered a major threat to crop and timber yields, with new diseases and pests likely to present new challenges to agribusiness. Defra has published a Tree and Plant Health Action Plan and pledged £7million to further research into diseases in plants.

The report also, controversially, highlights opportunities for the UK that these climate changes could present such as opening of arctic shipping routes and reduced cold-related deaths and illness during milder winters. The report suggests that food crops and fruit yields could improve if the problems related to flowing and disease are combated as a warmer climate would improve the major UK crops of sugar beet and wheat.

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3 Extreme weather motivates greener behaviour on Sun Aug 05, 2012 9:37 am

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People who live through extreme weather catastrophes are more concerned about climate change and are more willing to adopt greener habits to help tackle it, say environmental behaviour scientists.

Researchers at the Universities of Cardiff and Nottingham suggest that when individuals have experienced extreme weather events in their local area, such as flooding, they are more prepared to reduce how much energy they use in an effort to minimise climate change.

Britain has experienced a series of major flood events over the past decade and recent studies have linked rising greenhouse gases to an increased risk of flooding in England and Wales. Although no single weather event can be attributed to climate change, predictions suggest that extreme weather such as storms and floods are likely to become more frequent.

''We know that many people tend to see climate change as distant, affecting other people and places,'' says Alexa Spence, an environmental psychologist at the University of Nottingham.

''However, experiences of extreme weather events like flooding have the potential to change the way people view climate change, by making it more real and tangible, and ultimately resulting in greater intentions to act in sustainable ways.''

The research team asked 1,822 members of the British public what their personal experience of flooding were, what they thought about climate change, and if they were prepared to use less energy to help tackle it.

They found that people who had experienced floods had higher levels of concern about the impact of climate change, were less uncertain about whether it existed, thought their areas were more vulnerable to the consequences of global warming and were more prepared to reduce their energy levels.

In their paper, published in the journal Nature Climate Change, the researchers explain that local environmental changes could essentially provide ways of motivating people to take action on climate change.

''This important study provides the first solid evidence for something which has been suspected for some time – that people's local experience of climate related events such as flooding will promote higher awareness of the issue,'' says Nick Pidgeon, Professor at Cardiff's School of Psychology, who lead the study. ''As a result, it suggests new ways for engaging people with this most important and pressing of environmental issues.''

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4 Extreme Weather on Sun Aug 05, 2012 9:42 am

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It is clear by looking at historic records that the world has always experienced extreme weather events and climatologists tell us that we should reasonably expect to experience these up to 5% of the time.

Taking a few random 20th century examples of extreme weather:

In September 1900 a hurricane accompanied by a 15.7-foot storm surge hit Galveston in Texas. At the time Galveston had a population of 37,000 and around 20% lost their lives. At today's prices property damage was put at $700 million.
Between October 1923 and April 1924 Marble Bar in Western Australia experienced 160 consecutive days when the temperature topped 37.8°C (100°F).
In 1927 flooding in the Lower Mississippi claimed between 250 and 1,000 lives and left 700,000 homeless.
In 1974 Cyclone Tracy hit Darwin in Australia's Northern Territory, killing 71 people and destroying more than 70% of the town's buildings.
In October 1987 the worst storm hit southern England since 1703, causing 18 deaths and widespread damage. Such events are expected to happen only once in several hundred years, but three years later a similar storm of comparable intensity hit the UK.
The last ten years seem to have had more than the usual share of extreme weather events.

In January 2002 the temperature in the Australian state of New South Wales soared to 42.9°C (109°F). This was 8°C higher than the average summer temperature and it was hot enough to kill 1,453 flying foxes, or giant fruit bats.


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Hurricane Katrina hit South East Louisiana in late August 2005. It was the costliest natural disaster in US history. At least 1,836 people died in the actual hurricane and in the flood that followed after the levees failed. 80% of New Orleans was under water. Total property damage was estimated at $81 billion.
In July 2010 temperatures in Moscow reached 39°C (102°F) for the first time in recorded history. For 35 days the temperature reached at least 30°C (86°F) and more than 10,000 died in Moscow alone as a result of the sweltering conditions. Throughout that summer, wildfires raged out of control and 1.6 million acres were destroyed. The drought lasted right through July and August and 40% of the country's annual grain yield was lost.
In April 2011 yet another weather disaster hit the United States. This time at least 100 individual tornadoes descended on the states of Alabama, Mississippi, Arkansas, Tennessee, Georgia, Louisiana and Virginia. At least 310 people lost their lives and the storms caused billions of dollars in property damage.


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These are just four examples of extreme weather events occurring in the past ten years, but they are by no means isolated events. Since 2000 there have been a whole series of summer heat waves, winter freezes, tropical cyclones, tornadoes, wildfires, floods and everything else in between.

It is small wonder that people have begun to question whether or not this apparent increase in extreme weather events is due to changes in the world's climate pattern. The problem facing meteorologists is that extremes are not particularly good indicators of trends.

More comprehensive weather recording and enhanced awareness arising from current concerns about climate change means that events that in the past would have probably gone unnoticed are now widely reported. This lack of comprehensive historic record makes it very difficult to make accurate comparisons between past and present trends.

Weather forecasting, we are always being told, is an imprecise science. The problem facing scientists is deciding which weather indicators are useful and which are not. EUMETNET have set up the Meteoalarm website for extreme weather alerts in Europe.

There is still much that is not understood about the Earth's climate pattern and the various factors that influence our weather. However there is a strong and credible body of evidence, based on multiple lines of research that indicate a trend towards global warming.

This warming might well be part of a natural cyclical process. We know that the Earth experiences warmer and colder periods, but a careful scientific consideration of current available evidence convinces scientists that these changes are in a large part caused by human activities as larger amounts of greenhouse gases are released into the Earth's atmosphere.

Given that the world's climate is changing, the next question to be answered is whether or not the recent run of extreme climatic events is as a result of this, or whether it is purely coincidental.

In its publication: Weather extremes in a changing climate: Hindsight on Foresight the World Meteorological Organisation (WMO) points out that the years 2010, 2005, and 1998 rank as the warmest on record, with the last ten years also being the warmest ever recorded. It was also a decade marked by numerous weather and climatic extremes that were unique in both strength and impact.

WMO concedes that while it is impossible to say that an individual event was ''caused'' by climate change, it is reasonable to anticipate that the magnitudes, frequency and duration of extreme weather events are likely to be altered as the Earth's atmosphere warms due to the increased concentrations of greenhouse gases.


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The problem now faced by the world is what are we going to do about it?

Climate change is regarded as inevitable and there is nothing anyone can do about it. Switching off all emissions will not stop global warming, but if we can reduce the amount of greenhouse gas that we send into the atmosphere, this will reduce the pace of warming and slow down the number of extreme climatic events.

The world is highly vulnerable to meteorological extremes and the reduction of this vulnerability should be an essential target in the process of adapting to climate change, says WMO. Nations need to strengthen their research and their observing and monitoring capabilities. It is important to develop new methods if climate early warning and capabilities for climate system monitoring. And as a matter of urgency this should extend to the advancement of facilities in developing countries.

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Scientists have used computer models to answer the mystery of global warming's missing heat - and believe the answer lies deep beneath the surface of the oceans.
Scientists from the American National Centre for Atmospheric Research (NCAR) set themselves the task of explaining why as the emissions of greenhouse gases continue to rise there are breaks in the rise in global temperatures.

For example, while the first decade of this century was the warmest on record, the global single year record temperature, from 1998, wasn't broken until 2010 - global temperatures have not risen in a strict relationship with greenhouse gas levels.

"We will see global warming go through hiatus periods in the future," says NCAR's Gerald Meehl, who is the lead author of the study published in Nature Climate Change. "However, these periods would likely last only about a decade or so, and warming would then resume. This study illustrates one reason why global temperatures do not simply rise in a straight line."

Observations from space showed that the difference in the amount of heat coming into the planet from the Sun and the amount of heat radiated out from Earth had actually gone up, so where is the 'missing heat'? The team from NCAR and the Australian Bureau of Meteorology used complex computer models to test the hypothesis that the deep oceans were storing this energy.
Already, sea surface temperature measurements had suggested that the heat was warming the waters. Meehl and his colleagues used the Community Climate System Model, to try and predict how the climate would change when the actions of the whole climate system - the atmosphere, oceans, sea ice and land - were considered.

Their work found, in one of five examples, that a global temperature rise of 1.4 during this century was accompanied by two pauses in warming of a decade each as the deepest parts of the ceans (below 300 metres) took on a much larger share of the extra heat, warming by close to 20%.

"This study suggests the missing energy has indeed been buried in the ocean," said Kevin Trenberth, who with fellow author of this report John Fasullo was behind the first work suggesting deep ocean warming. "The heat has not disappeared, and so it cannot be ignored. It must have consequences."

Those consequences could, the researchers believe, be related to the El Nino and La Nina phenomena, with La Nina corresponding to deep ocean warming periods. Both the Pacific warming of El Nino and the cooling of La Nina are associated with extreme weather events.

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In some ways, the recent letter by 16 scientists to the WSJ, claiming that there is 'no need to panic about global warming', is indeed reassuring. The very fact that this slice of global warming skepticism has attracted such a feeble number of scientists - of whom only 2 have published in the climate science field recently - shows how global warming denialism has failed to gain any traction in the scientific community.

But the global warming debate matters most, not in the rarefied sphere of climate science, but in the hurly-burly world of opinions formers and political spinmeisters. And there, for the last few years, the climate skeptics have had a much better run at things. Charges have been flung, mud has stuck, and doubt been cast. For many, across the political spectrum, climate change is now a dirty word. And far less of the public is concerned about the threat from global warming than was the case 3 years ago.

Much of this softening of opinion comes from a confusion about whether global warming is real - or whether it really heralds such a looming calamity. So in that sense, worthy-seeming letters, signed by scientists who question the need for action on climate change, really do matter. They keep open the illusion that the science on global warming is still 'unsettled'. That's why its worth digging deeper into the claims made in the WSJ piece, to help separate reasonable doubt from unjustified claim. Sadly, though, there appears to be very little of the former in this skeptics' letter.

There are just two solid claims made in this article. The rest is a reworking of accusations of scientific witch-hunts and collusion between money-grabbing climate scientists, and big bad government. However, given how conspiracy theories have a life of their own, which readily defy any attempts rational argument, let's pass those by - and focus instead on the more concrete claims.

The first is that global warming is much less of a scary monster than the 'alarmists' have painted - and may even have shrunk to a poodle over the last decade. 'Perhaps the most inconvenient fact is the lack of global warming for well over 10 years now,' say the 16, repeating a common skeptic mantra. One, however, that shows a woeful misunderstanding of what 'global warming' means. While it is true that 1998, 14 years ago, was one of the warmest years on record - and that many years since have been a little cooler - drawing lines between cherry-picked point on the graph does not define global warming or cooling.

The global thermometer runs up and down, year-on-year, for any number of natural reasons - the cooling from volcanic eruptions, changes in the radiation coming in from the sun, or yearly flips between warmer El Nino and cooler La Nina years. To get a proper feel for the longer-term energy being trapped by greenhouse gases, you need to smooth out those cycles. One approach is to average out global temperature points over longer time-frames - 17 years is an accepted convention. Another is to subtract the known effect of those natural changes from the global temperature graph.

That's what was done in a recent paper by Grant Foster and Stefan Rahmstorf, in the journal Environmental Research Letters. They took 4 of the most widely used measures of global temperature, and then carefully removed the cooling kicks and warming nudges, from the things like last year's strong La Nina - or the dust thrown up by the dramatic Mount Pinatubo eruption. The resulting temperature graph is one of a relentless rise - and shows little sign of any let-up in global warming over the last decade:

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Paper includes average of all five data sets (GISS, NCDC, HadCRU, UAH, and RSS) with the effects of ENSO, solar irradiance, and volcanic emissions removed (Foster and Rahmstorf 2011)

The other claim - following on from this less-than-convincing rubbishing of global warming's onward march - is that even if global warming is happening, the 'modest' temperature rises seen require no action. That's based on research by William Nordhaus, an economist who looked at the costs-and-benefits of tackling global warming, compared to just letting economic growth continue unfettered. It 'showed that nearly the highest benefit-to-cost ratio is achieved for a policy that allows 50 more years of economic growth unimpeded by greenhouse gas controls,' they say.

But for this claim to have any validity, the assumptions underlying Nordhaus' economic models would need to hold over the next five decades. And you would have to believe that the well-being of the planet, and of humanity, can be reduced to the slide-rule accountancy of the economics. Both of those points seem contentious.

Economic models have been shown to melt like snow in the sun - just look at how the captains of the global economy were short-footed by the credit collapse of 2008-9. In fact, economic models can make climate models seem like cast-iron certainties, in comparison. And can economic growth really can carry 'unimpeded'? That seems unlikely, when the last few years have shown how depleting resources can smother smug notions of endless economic growth.

Far more problematic, for the 'cost-benefit' analysis of Nordhaus and his ilk, is the essentially unpredictable nature of the climate change experiment we are undertaking. Of course it's possible that the consequences of global warming will be easier to deal with than many suspect. It is also possible that the consequences could be far worse. We are tampering with a system that the WSJ sixteen admit is poorly understood - a system on which all our futures depend. When there are routes to a greener, safer, cleaner future, which can readily reduce those risks, surely it would be madness to forge on regardless our current reckless path?

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The phrase 'global warming' has been thrown about so much, in the ongoing debate over dangers of man-made climate change, that it can seem more like a dark shadow on the horizon, than an imminent threat. But if the weighty evidence of thousands of scientific papers over the last two decades is to be believed, global warming isn't just real and happening now - its negative consequences are being played out all around us, affecting the lives of millions. So what exactly do we know about the effects of global warming on our planet in the here-and-now? And how will our futures be affected, as the global thermometer continues to rise?

Global warming - tortoise or hare?

One of the many confusing aspects of global warming is the very phrase itself. 'Global warming' was coined by climate scientists to describe the biggest knock-on from the increase in man-made greenhouse gases. As a whole, and averaged out over decades, the amount of heat trapped in the earth's atmosphere will gradually increase - in tandem with the rising levels of CO2 and other greenhouse gases. And years of painstaking temperature measurements from thousands of weather station records, have confirmed a slow inexorable rise in that overall temperature across the globe.

But while 'global warming' itself sounds big and scary, the actual numbers put to the planet's average temperature rise sounds rather small - maybe 1˚C averaged out over a century. Which sounds more like a tortoise than a hare, and so maybe not so scary a problem after all. However, it's not the slow rise of that difficult-to-measure global thermometer that's the problem. It's how that extra energy in the atmosphere knocks through to the rest of the climate - which we experience as weather - that is having the biggest impact on us all.


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Hotter, wetter, wilder - the new normal?

Of course, the most obvious impact on us from global warming is a rise in the temperatures we experience day-to-day. However, that effect isn't felt 'in average' - it is being felt across the world's climate regions in a widely varying manner. Some parts of the globe are experiencing a rapid temperature increases - for example the Arctic, which has seen dramatic rises of over 2°C in the last 30 years - others less so. And while most places are hotting up, a few are actually experiencing temporary cooling, such as parts of Antarctica.

The temperature changes are also happening at a faster rate than the planet has experienced in millions of years. Unused to this speed of change, major stress is being caused to the natural world - from ocean life, to trees, to birds. And because we depend for our food and water on the health of the world's ecosystems, those stresses are being felt by us too. So rising temperatures are already reducing food harvests, threatening fish stocks, and drying water sources.

And the problems with the heat don't stop there. Scientists predict that, not only will much of the globe see gradually rising temperatures, but extreme temperature spikes - such as heat-waves - will become much more common; and much more extreme. The destructive potential is well-illustrated by 2010's Russian heatwave, which saw 9 million hectares of crops destroyed, and 10,000 excess deaths. That extreme weather event has been linked conclusively to global warming.

It's not just extra heat that we are all having to deal with. The way water is moved around the from sea to atmosphere is changing too. The amount of rain that can fall from the skies is tied to how much water vapor is stored in the atmosphere. As the temperature of the air rises, it can hold more water vapor. So global warming charging up weather systems, allowing storms to dump greater volumes of water down upon our heads, so increasing the risks of flooding. Recent unprecedented floods in the Mississippi basin, Thailand and Pakistan may have had a helping hand from global warming.


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Seas on the move

While the rising temperatures of global warming may be pushing the atmosphere towards greater extremes of weather - with all the destructive potential that implies - that extra heat is also having an effect on the oceans. As the oceans warm, they are expanding and swelling, so pushing sea levels higher. Add to that the extra water flowing into the seas from melting glaciers and land-locked ice-sheets, and global warming can be seen as the culprit for threatening the safety of low-lying coasts.

Again, it's not the gradual long-term rise in sea-levels that is a direct threat - thought to amount to as much as 1 meter, or 3 feet, over the next century - but how that higher base-line affects the natural 'sloshing about' of sea. The level of the sea is constantly on the move, in response to the tidal pull of the moon, and the heightening affect of low-pressure weather systems. That random rippling sea-level already causes occasional flooding risk to coastal communities, especially when storms push walls of sea-water ahead of them in 'surges'. But with average sea-levels inching higher, those storm-surges will be more common, go further inland, and be more destructive.


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The unknown unknowns

While all of the above effects are serious enough - and are causing the most distress to those parts of the planet least able to deal with them - it is the changes we don't know about that are perhaps the greatest threat. Global warming is shifting climate patterns in ways we find difficult to predict. Ice sheets are melting faster than forecast and could disappear; tropical rain-forests such as the Amazon may be dried-out and decimated by shifting rainfall patterns; or the greenhouse gases locked up in the Arctic oceans could be released in a great methane belch.

Even one of these events could result in dramatically more serious consequences for the planet, and its inhabitants - which includes us. We already have a good understanding of the risks we are living with, because of global warming so far. But it is the dangers of these unknowable risks from future warming that should weigh heaviest, in the ongoing debate over global warming and climate change.

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