Climate change is the biggest challenge of the 21st century. It threatens the well-being of hundreds of millions of people today and many billions more in the future. It is also a significant threat to our economy and critical infrastructure. And one of the main causes of climate change is our addiction to fossil fuels – coal, oil and gas.
No-one and no country or region, ours included, escapes the impact of climate change. But it is the poorest people in societies who are most vulnerable. This is what makes it an ethical as much as a scientific or economic issue.
Given the compelling weight of peer-reviewed scientific evidence, it can be hard to understand why anyone denies climate change or drags their feet about the urgent and co-ordinated action needed to reduce greenhouse gas emissions.
Last September, the Intergovernmental Panel on Climate Change stated clearly that the "warming of the climate system is unequivocal" and that human behaviour is extremely likely to be the dominant cause.
Recent months have also brought examples – from devastating typhoons in the Philippines, to the polar vortex in North America and widespread floods here in Northern Ireland – of the increase in extreme weather events that is the inevitable outcome of climate change.
The costs are already enormous, which is why organisations ranging from the World Bank, the International Monetary Fund and the International Energy Agency and insurance companies such as Lloyds of London have joined the scientific community in warning about the risks. It is no longer only Greens ringing alarm bells.
Every year, we fail to act. To move away from a fossil fuel-based economy brings us closer to the tipping point when scientists fear runaway climate change.
But acting now and decisively to combat climate change can bring many benefits.
We have reached a fork in the road. In one direction, a terrible legacy could be handed to future generations.
In the other, is the opportunity to set our world on the first steps toward a fairer and sustainable future for the common good.