Planet likely to warm by 4C by 2100, scientists warn. We ignore the disastrous storms in the Caribbean at our peril.

Planet likely to warm by 4C by 2100, scientists warn

New climate model taking greater account of cloud changes indicates heating will be at higher end of expectations

Damian Carrington

The Guardian, Tuesday 31 December 2013 / http://www.theguardian.com/environment/2013/dec/31/planet-will-warm-4c-2100-climate

Temperature rises resulting from unchecked climate change will be at the severe end of those projected, according to a new scientific study.

The scientist leading the research said that unless emissions of greenhouse gases were cut, the planet would heat up by a minimum of 4C by 2100, twice the level the world's governments deem dangerous.

The research indicates that fewer clouds form as the planet warms, meaning less sunlight is reflected back into space, driving temperatures up further still. The way clouds affect global warming has been the biggest mystery surrounding future climate change.

Professor Steven Sherwood, at the University of New South Wales, in Australia, who led the new work, said: "This study breaks new ground twice: first by identifying what is controlling the cloud changes and second by strongly discounting the lowest estimates of future global warming in favour of the higher and more damaging estimates."

"4C would likely be catastrophic rather than simply dangerous," Sherwood told the Guardian. "For example, it would make life difficult, if not impossible, in much of the tropics, and would guarantee the eventual melting of the Greenland ice sheet and some of the Antarctic ice sheet", with sea levels rising by many metres as a result.

The research is a "big advance" that halves the uncertainty about how much warming is caused by rises in carbon emissions, according to scientists commenting on the study, published in the journal Nature. Hideo Shiogama and Tomoo Ogura, at Japan's National Institute for Environmental Studies, said the explanation of how fewer clouds form as the world warms was "convincing", and agreed this indicated future climate would be greater than expected. But they said more challenges lay ahead to narrow down further the projections of future temperatures.

Scientists measure the sensitivity of the Earth's climate to greenhouse gases by estimating the temperature rise that would be caused by a doubling of CO2 in the atmosphere compared with pre-industrial levels – as is likely to happen within 50 years, on current trends. For two decades, those estimates have run from 1.5C to 5C, a wide range; the new research narrowed that range to between 3C and 5C, by closely examining the biggest cause of uncertainty: clouds.

The key was to ensure that the way clouds form in the real world was accurately represented in computer climate models, which are the only tool researchers have to predict future temperatures. When water evaporates from the oceans, the vapour can rise over nine miles to form rain clouds that reflect sunlight; or it may rise just a few miles and drift back down without forming clouds. In reality, both processes occur, and climate models encompassing this complexity predicted significantly higher future temperatures than those only including the nine-mile-high clouds.

"Climate sceptics like to criticise climate models for getting things wrong, and we are the first to admit they are not perfect," said Sherwood. "But what we are finding is that the mistakes are being made by the models which predict less warming, not those that predict more."

He added: "Sceptics may also point to the 'hiatus' of temperatures since the end of the 20th century, but there is increasing evidence that this inaptly named hiatus is not seen in other measures of the climate system, and is almost certainly temporary."

Global average air temperatures have increased relatively slowly since a high point in 1998 caused by the ocean phenomenon El Niño, but observations show that heat is continuing to be trapped in increasing amounts by greenhouse gases, with over 90% disappearing into the oceans. Furthermore, a study in November suggested the "pause" may be largely an illusion resulting from the lack of temperature readings from polar regions, where warming is greatest.

Sherwood accepts his team's work on the role of clouds cannot definitively rule out that future temperature rises will lie at the lower end of projections. "But," he said, for that to be the case, "one would need to invoke some new dimension to the problem involving a major missing ingredient for which we currently have no evidence. Such a thing is not out of the question but requires a lot of faith."

He added: "Rises in global average temperatures of [at least 4C by 2100] will have profound impacts on the world and the economies of many countries if we don't urgently start to curb our emissions."

Flood-hit Colombia in 2011, when the rain almost never stopped

We ignore the disastrous storms in the Caribbean at our peril

Storms have taken lives in the Caribbean, and caused chaos in the UK – climate change is eroding certainties across the globe

Carrie Gibson

theguardian, Tuesday 31 December 2013 / http://www.theguardian.com/commentisfree/2013/dec/31/storms-caribbean-uk-climate-change

As tens of thousands people suffered through a flooded and powerless Christmas in Britain, 5,000 miles away unexpected weather was also unleashing havoc on the Caribbean.

Torrential rains on Christmas Eve, with 15in falling in 24 hours, led to dramatic floods and landslides that washed through St Vincent and the Grenadines, St Lucia and Dominica. So far eight people in St Vincent and five in St Lucia have died, water and electricity are down and thousands of properties have been damaged. The clean-up bill is expected to be in the millions.

The crisis cut short the holiday of the prime minister of St Vincent, Ralph Gonsalves, who happened to be in storm-hit London, after a trip to see the pope in Rome. Gonsalves – whose cousin was killed in a landslide during the rains – said it was "a disaster of a proportion the likes of which we have not seen in living memory". The secretary general of the Organisation of American States, José Miguel Insulza, also noted the "unreasonable nature" of the rains, and said "the flooding raises once again the impact of climate change in the Caribbean region".

Many years ago, during a rainy spell in Britain, a South African colleague at my office grumbled that Britain didn't have a climate – it only had weather. I chuckled at the time, but it seems that this now goes well beyond the UK. Unmoored from what usually happens during a given season, we are increasingly vulnerable to the brutal force of extreme weather events at short notice.

The Caribbean's climate does involve a rainy period – it is part of the hurricane season, which starts around June and usually lasts until around mid to late November. The 2013 hurricane season was the quietest in 30 years, with only two storms, and they did not even reach an intensity of category three or above. With regards to these recent rains, public opinion appears to agree with Gonsalves: these downpours were unprecedented.

There is no doubt that something is amiss in the tropics, and has been for some time. For instance, in 2011 in the north-east region of Colombia, the rain almost never stopped, and floods devastated the country, with hundreds of thousands of homes damaged and millions of people left suffering. And Trinidad and Tobago, too, has been experiencing severe and often unexpected flooding in the past few years, due to heavy rains.

The Caribbean is on the receiving end of the effects of climate change – it has to adapt and respond to the consequences, even though it has contributed little to the problem. Like other island nations, rising sea levels are a particular threat. A recent report by the Inter-American Development Bank claims that the tourism industry could lose some $900m a year (£550m) by 2050, and that flat, non-volcanic islands like the Bahamas are considered especially vulnerable.

There is also the risk that more people on the islands will choose to live abroad – if they are not evacuated first. But erosion is not something from a computer model – it's happening now. For instance, Varadero, Cuba – where more than a million tourists descend every year – has lost between 40,000 and 50,000 cubic metres of shoreline (430,000 to 537,500 sq ft), and a recent report says around 84% of the island's beaches are threatened.

For the Caribbean, unpredictable weather and eroding beaches could harm the vital tourism trade. In addition, the islands have a range of environmental issues to tackle, from mining in Jamaica to deforestation in Haiti. There is a rich ecosystem across the region – forests and biodiversity above water, and precious coral reefs and aquatic life below – that is increasingly under threat. The islands are trying to cope, earmarking scarce funds to deal with these challenges, set against a backdrop of economic struggle and often poor infrastructure. But moves have long been under way in places such as Belize, Dominica, and Costa Rica to encourage eco-tourism. The Caribbean Community Climate Change Centre was set up in 2005, which involves most of the Caricom members (18 of the English-speaking states of the Caribbean, as well as Haiti and Suriname), and most islands have scientists monitoring changes in climate patterns, and taskforces to attempt to deal with the consequences.

Whatever you think about climate change, the onset of erratic and extreme weather erodes any pretence of certainty. Modern life, as recent events in Britain have shown, has no time for floods, storms, downed power lines, delayed trains or flights – but this is our future. So in this sense, small islands, whose tribulations are often are ignored, are really the canaries in the coal mine.

This Christmas the impact of climate change reached across the Atlantic: developed and developing worlds were brought together in a misery of rising flood waters. We ignore what is happening to the places on the frontline of this changing climate at our peril.