The floods in Colombia in 2010, which killed 174 people and left 1.5 million homeless, concentrated the minds of policy-makers on climate change as never before. President Juan Manuel Santos said there had ‘never been a tragedy of this scale’ in the country’s history.

In North America this year, a combination of drought in California and severe winter storms on the East Coast has had the same effect. Secretary of State John Kerry made a powerful speech in Jakarta on 16 February in which he said that ‘in a sense, climate change can now be considered the world's largest weapon of mass destruction, perhaps even, the world's most fearsome weapon of mass destruction’.

In the UK also, there have been severe winter floods, on a much smaller scale than Colombia’s, but nevertheless resulting from the wettest winter for over 100 years and the worst sequence of winter storms for two and a half centuries. The Prime Minister, David Cameron, told parliament that he ‘very much suspects’ climate change was a factor behind these extreme events. Prince Charles, a long-standing environmental activist, has described climate change sceptics as ‘the headless chicken brigade’.

You might think that climate sceptics would be silenced by this combination of tangible phenomena and high-level political engagement.

However, you would be wrong. In the US, no less a figure than Newt Gingrich has called for Secretary of State Kerry to resign because of his remarks on climate change. In the UK, former Chancellor of the Exchequer Lord (Nigel) Lawson has denied that the floods have anything to do with the climate, and has called for an end to the building of wind turbines in the British countryside.

And Gingrich and Lawson are not alone. In the US, for example, public opinion research by the Pew Foundation in January 2014, showed that climate change ranked second to last among twenty priority issues for the President and Congress. In Europe, the numbers may be more favourable, but recent polling in the UK shows that 39% of people do not believe the flooding was caused by climate change.

These numbers show that proponents of action on climate change need to work harder to make the science accessible – and to demonstrate that the initial impacts are already being felt. Specifically, they need to counter the argument that the apparent pause in warming over the past fifteen years indicates that long-term warming is not (yet) a threat.

The scientific evidence has been brought together in the latest report of the Inter-Governmental Panel on Climate Change, published in January 2014. More than 850 authors contributed to the Report. Its findings are unambiguous. In careful language, the IPCC says that

• ‘Warming of the climate system is unequivocal. . . Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850. The globally averaged combined land and ocean surface temperature data as calculated by a linear trend, show a warming of 0.85°C, over the period 1880 to 2012.
• Ocean warming accounts for more than 90% of the energy accumulated between 1971 and 2010. . . The annual mean Arctic sea ice extent decreased over the period 1979 to 2012 with a rate that was very likely in the range 3.5 to 4.1% per decade, and summer sea ice minimum very likely in the range 9.4 to 13.6%.
• The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia. Over the period 1901 to 2010, global mean sea level rose by 0.19 m.
• Finally, the atmospheric concentrations of carbon dioxide, methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. Carbon dioxide concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions.‘

The IPCC report is a consensus-based and systematically peer-reviewed document and inevitably takes time to catch up with the latest research. However, new research shows a strong link between climate change and current extreme events. As Dame Julia Slingo, the Chief Scientist of the UK Meteorological Office has observed: ‘all the evidence suggests there is a link to climate change’. The Met Office has also dismissed the evidence that the pause in warming means that climate change is not happening in the long term. And researchers in Australia and the US have shown that the pause in warming may be caused by changes in trade winds over the Pacific Ocean.

Are you convinced? I am. And if we are, why aren’t the climate sceptics, whether in leadership positions or not? Are they all ‘headless chickens’?

Perhaps there are no laggards in Latin America. Public opinion research, again by the Pew Foundation, carried out in mid-2013, showed concern for climate change at 65%, as high as anywhere in the world. Latin American leaders have been at the forefront of the global argument.

Nevertheless, just in case any sceptics remain, we can bring people over to the other side of the argument, by doing three things.

1. First, by making sure that the analysis of the impacts is as strong as the analysis of the physics. The IPCC has this in hand, and will be publishing reports on impacts in 2014, leading to the publication of its overall synthesis report in October. The direct and indirect costs of drought and floods will feature, as will the longer term impacts on health and economies. Latin America will certainly be among those most affected, as the IPCC has already Remember the key finding of the Stern Review in 2006 on the economics of climate change, that climate change could cost 5% of global GDP. That is about $US 3.6 trillion a year, or $US 500 a year for every man, woman and child on the planet. Stern now says the cost of inaction may be underestimated.

Second, by finding better ways to make the case: not just with numbers and graphs, but with pictures and human interest stories. Not for nothing is the polar bear the poster child of the environmental movement. What is the equivalent in Colombia, I wonder? Perhaps the toucan? Or the spectacled bear, the iconic symbol of Colombia’s National Parks?

Third, by looking for the silver lining in the rain-bearing clouds – creating not a negative message of imminent catastrophe, but a positive vision of economic transformation. There will be new jobs in the green economy, and there can be a better life for all. Imagine a world, for example, with less traffic congestion and less air pollution.

And if these three strategies are not enough to convince the sceptics, especially those in leadership positions? Well, the best place for the headless chickens might be tucked up in the chicken coop.

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Photo: http://tinyurl.com/oaatlbj