Today, one part of the climate change debate comes to an end. The scientific debate is over. The IPCC, a huge distinguished panel of international climate scientists, has concluded that to limit climate change, the world must make a continued and substantial reductions of greenhouse gas emissions. No other scientific conclusion has been subjected to such prolonged,detailed, global scrutiny. Those responsible for our media coverage – particularly the BBC – should take note.
Time should be called on a long, rancorous, and frequently very odd debate, in which a tiny number of individuals and small groups – frequently with clear vested interests - have been given equal weight to 97 per cent of climate scientists. The Flat Earth Society still exists, but that doesn’t mean we have to take them seriously.
Of course it’s not just climate scientists – and green campaigners - who’ve recognised the pressing urgency of action on climate change. From the head of the IMF, Christine Lagarde, who said climate change kept her awake at night , to 83 per cent of Global 500 companies  which have recognised climate change as a serious risk to their operations, to the heavily at-risk inhabitants of fragile small island nations around the globe, there’s wide understanding. As Ban Ki-Moon, UN Secretary-General has said : “"The heat is on. Now we must act."
Those opposed to “green” action in Britain often say that we can’t afford it in today’s economic climate. On the contrary, we can’t afford not to act for the sake of both economy and environment. And that’s not just because of the risk of the floods, the droughts, the heatwaves, are already having huge human and financial costs, but because of the weaknesses and the failures of the very foundations of our economy and everyday life, structures built on massive consumption of once-cheap fossil fuels that we can no longer afford.
We have a huge problem with fuel poverty in Britain, the result in part of rising energy prices – almost all due to the rising cost of gas and distribution costs in our privatised system, but also of our leaky, poor insulated homes. With not a penny of government funds currently going into home insulation, we’re not only missing out on tackling that problem – but also creating tens of thousands of good, long-term jobs, as well as cutting carbon emissions.
We have a huge problem with unemployment, under-employment and low pay in Britain. Investing in and developing renewable energy generation technologies – based around our rich wind and tidal power sources – offers the chance to generate.
The Centre for Alternative Technology has calculated that together renewable technologies and energy conservation can deliver up to 1.5 million good new jobs.
We have a huge problem with food poverty in Britain – with half a million people dependent, today, on food banks to get enough to eat. We need to bring food production back to Britain, restoring the ring of market gardens around our towns and cities, ensuring food security in our increasingly uncertain world, removing currency risk. We must end the dreadfully wasteful, destructive practice of air freighting fruit and vegetables, and cutting down our practice of shipping them around the world.
We have a growing problem of “transport poverty” in Britain – fast rising rail and bus fares that are trapping our often forced commuters into further poverty. We need to develop a transport plan for England ' built at its base around walking and cycling (worth noting that 1.3 million more new bicycles  were bought last year in Britain than cars registered), with affordable, reliable, timely public transport available for longer journeys. Again, more good jobs, as well as cleaner air and better public health.
There are also looming threats that we need to avert. Green MP Caroline Lucas has highlighted the economic threat of the “carbon bubble” – the unburnable fossil fuels whose valuation underlies the stock prices of some of our largest companies. We need to think long and hard about how to manage that risk, how we can keep more than half of our known fossil fuel reserves in the ground, not subsidise the potential new and risky operation of fracking for shale gas, as our government is currently doing.
It’s not surprising that we’ve seen uncertainty about climate change growing in Britain, with a recent poll  showing 19 per cent of people were not sure about the human cause of it. (Although of course 72 per cent were sure). With the government failing to take action, with a Lib Dem energy secretary saying he “loves” shale gas , some people understandably thought that perhaps climate change was something they didn’t have to worry about. But they, and the government, have today been given a wake-up call.
Britain has been a leader, and we can, and must, be again. In passing the 2008 Climate Change Act, Britain stood out in declaring its collective intention to reduce greenhouse gas emissions. Now we need to match that with action.
Natalie Bennett is the Green Party leader