Extreme weather and rising seas are already global threats. This will only intensify
World leaders will meet in Paris this year to try to reach a deal to cut carbon emissions. Failure could be catastrophic. We explore the facts, myths and opinions around global warming, starting with an expert view and a survey of the British public by Opinium/the Observer You may not realise it from the UK general election campaign, but this is a crucial year for the global battle against climate change. Governments are increasing their efforts to secure a new international agreement at the United Nations summit in Paris in December to avoid a dangerous rise in global average temperature. A strong treaty is still possible, but, while there is recognition that rising greenhouse gas levels are creating a problem, there is still not enough understanding of the scale of the action required, or the opportunities that a transition to a low-carbon economy offer for growth and poverty reduction. There is mounting evidence across the world of the growing impacts of climate change. Last year was the warmest on record globally, with 13 of the 14 hottest years now having occurred since 2000. And the period between January and March 2015 has been hotter than any other year. In the UK, 2014 was our warmest year , with the eight warmest years all having taken place since the start of the new millennium. Because a warmer atmosphere can hold more water, we are also experiencing heavier rainfall. The winter of 2013-14, during which there was devastating flooding in many parts of the country, was the wettest we have ever seen . More frequent and severe extreme weather, rising sea levels and acidifying oceans are already posing threats to homes and businesses across the world, yet global average temperature has only risen by less than one centigrade degree. Over the next few decades, climate change will intensify further as the Earths atmosphere, land and oceans adjust gradually to current levels of greenhouse gases, and we will have to adapt. But the state of the climate in the second half of this century and beyond will depend on decisions we make this year. Delay and inaction on emissions will be dangerous. If we fail to put the world on a path towards low-carbon economic growth and development, the lives and livelihoods of billions of people will be at risk, as global temperature rises beyond anything the Earth has experienced over the past few million years. That is why governments agreed in 2010 in Cancun, Mexico , that global warming of more than two degrees would be unacceptably dangerous. This figure was chosen because research shows that if the climate warms by more than two degrees, it may unleash a series of unstoppable processes such as the melting of polar ice sheets, the death of the Amazon rainforest and a release of carbon from global soils that would lead to a further acceleration of warming. But so far, countries have not committed to the emissions reductions required to give a good chance of preventing temperatures from exceeding that limit. So during the past few years, governments have been engaged in detailed negotiations over a new agreement that can achieve that limit. Last December, in Lima, Peru , they reached a collective decision to put forward before the Paris meeting their pledges for action after 2020. So far, 35 countries have submitted so-called intended nationally determined contributions, including the 28 member states of the European Union and the US. In addition, China has pledged to slow the growth of its annual emissions to reach a peak no later than 2030. When the actions of China, the US and the EU are put together, and combined with assumptions about other countries plans, they suggest that the annual global output of greenhouse gases from human activities in 2030 should be much lower than would be the case under a scenario of unchecked emissions. But these pledges are still far above what would be consistent with an emissions pathway that would offer a reasonable chance of limiting global warming to no more than two centigrade degrees. This gap does not mean the Paris summit is already a failure. The commitments by China, the US and the EU can be delivered through their domestic policies, and legal and administrative structures. And there is a track record; they are likely to deliver on their commitments on emissions made in Cancun, Mexico in 2010. That is, their pledges are credible. However, the magnitude of the gap makes it obvious that the agreement in Paris must create an ongoing process through which countries will subsequently evaluate progress, learn from experience and increase the strength of their emissions cuts. The Paris agreement must also include other important features if it is to result in the successful management of the risks of climate change. In particular, it must embody support, including public and private funding, from the rich countries to help developing countries to build low-carbon economies, and to become more resilient to those impacts of climate change that cannot now be avoided. The strength of the commitments put forward by developing countries for Paris, and their willingness to ramp up ambition afterwards, will depend on the extent to which they are given financial and technological backing by the rich countries. Any commitments made in Paris must also take account of the important outcomes of the meeting in Addis Ababa in July on financial support for development of the worlds poorest countries, and of the UN general assembly in September where the millennium development goals will be succeeded by new sustainable development goals . Together, these events in Paris, Addis Ababa and New York in 2015 provide crucial opportunities to make decisive progress on the two biggest challenges facing humanity: overcoming poverty and managing climate change. Over the next 15 years, developing countries are expected to spend about two-thirds of the $90trn that the world will invest in infrastructure. If this locks in a dependence on fossil fuels and high-carbon growth, it will be impossible for the world to reach an emissions pathway consistent with avoiding dangerous climate change. Without sound economic policies, fossil fuels are badly underpriced. There are huge real costs, not reflected in the market, from burning fossil fuels because they create air pollution and climate change. There is growing recognition of the pernicious effects the consumption of fossil fuels creates through air pollution. As the Global Commission on the Economy and Climate pointed out last year, fine particles from burning coal and diesel are costing China the equivalent of more than 10% of its gross domestic product each year through premature deaths and ill health. And in Germany, the costs of air pollution are about 6% of annual GDP. Further, as countries pursue the goal of lower emissions, we are seeing extraordinary technical progress and learning about low-carbon technologies. This means that, as countries start to seize more of the substantial economic opportunities from progressing to cleaner and more efficient economies, they will be able to further reduce their greenhouse gas emissions. There are many signs that this is happening. China, for instance, cut its consumption of coal in 2014 while also substantially increasing its electricity generation from renewable energy sources, such as wind and solar. And in the UK, we managed to reduce our annual emissions by an impressive 8.4% between 2013 and 2014 by using lower amounts of dirty energy, and without compromising economic growth. Globally, there are huge investments being made in alternatives to fossil fuels which should allow us to slow and reverse the growth in annual emissions. According to the international energy agency, more than a fifth of the worlds electricity is generated from renewable energy, and more than $250bn is being invested in these sources annually. While this provides some grounds for optimism, the road to Paris will still be challenging. The governments of some countries, such as Australia and Canada, appear to be gambling against the science. Developing countries remain deeply critical of the irresponsible behaviour of these and other rich countries that are shirking their responsibilities. They rightly insist that any agreement in Paris must be fair and equitable, and their willingness to commit to alternative low-carbon routes to economic growth will depend on support from the rich countries. So it is not yet certain that this year will provide the turning point in the worldwide battle against climate change, but the chances will be greater if the citizens of the UK and other countries put pressure on their governments to seek an ambitious international agreement. The public opinion survey conducted by Opinium/the Observer reveals that only 20% of the UK public think it is likely that the politicians and world leaders will agree a long-term plan that will keep global warming within acceptable levels. Such pessimism is understandable given the slow pace of progress, but we should beware of allowing it to become a self-fulfilling prophecy. The same poll showed strong support for the UKs landmark Climate Change Act and policies to cut our emissions, and all of the major political parties seeking votes in the general election have promised in their manifestos to continue efforts to curb greenhouse gases. If we lead by example, we will be able to seize the opportunities to create a stronger, cleaner and more efficient economy. We can take the opportunity to build cities that work and energy systems that are reliable and clean. We can show other countries the benefits of moving away from the destructive high-carbon path. And we will ensure that we leave a legacy to our children, grandchildren and future generations of a safer and more prosperous world. Nicholas Stern is chair of the Grantham Research Institute on Climate Change and the Environment at the London School of Economics and Political Science, and president of the British Academy. His new book, Why Are We Waiting? The Logic, Urgency and Promise of Tackling Climate Change , will be published by MIT Press on 15 May.