The government’s failure to tackle climate change is “reckless and short-sighted” with just 50 months remaining to prevent a critical threshold in the fight against global warming being breached, environmental campaigners warn today.

In a letter to the Guardian and expanded on in an article in G2, they say global warming remains one of the greatest threats to human progress but condemn the fact it has dropped down the political agenda. The signatories, including senior figures at Greenpeace, Oxfam and the Women’s Institute, as well as the designer Dame Vivienne Westwood and the environmental campaigner Bianca Jagger, warn there are just 50 months left before it will become unlikely that a 2C temperature rise can be prevented. The UK and the EU have set the 2C mark as a line the world should not cross.

“There is so much to gain from investing with speed and scale in a modern, low-carbon economy, that the failure to do so appears both reckless and short-sighted,” the letter says. “Some recent policies seem even to take us backwards. More of the same old economics will not work. To create jobs, more secure energy systems and less pollution, investing in a massive energy-efficiency drive, and a programme to expand renewable energy are just two of the more obvious steps that could benefit the economy and the environment.”

The campaigners say the lack of action comes against a backdrop, this year, of a record loss of sea ice, greenhouse gas concentrations above the Arctic at their highest point for possibly 800,000 years, and crop-wrecking droughts and record temperatures in the US mid-west.

The signatories have outlined to the Guardian what they will do differently over the next 50 months to prevent the threshold being breached and challenge the government and opposition to do the same. Ruth Bond, chairwoman of the National Federation of Women’s Institutes, will try to give every child practical skills such as cooking to tackle obesity and instil the value of food, and growing food, which gives them an appreciation of the natural environment.

John Sauven, executive director of Greenpeace , has committed to more direct action to protect the Arctic from oil drilling, while Westwood said there was a need to inflame public opinion and blame politicians for the crisis.

The letter urges politicians to say what they will do “to grab the opportunity of action and prevent catastrophic climate change”.

Flood pictures are miserable and frightening as this week has shown yet again, with more than 400 homes and businesses inundated, most of them in the north of England. But there is another sort of image which the government would do well to consider, especially during a time of relentless recession.

Flip back through the albums and newsreels to the work of the Tennessee Valley Authority in the US, started in 1933 by President Franklin D Roosevelt as one of his first and biggest responses to the Great Depression. Then Photoshop the grainy pictures of recovering farmland and celebrating small-town communities on to the current backdrop of the swamped Vale of York or evacuated houses in Newcastle.

This is putting two and two together in a fashion as simple but as justified as the words of the Sunday school chorus from Cliff College in Derbyshire: “The rains came down / And the floods came up.” Every indicator, from the government’s own climate change report to the unprecedented loss of this year’s Great Yorkshire Show in a sea of mud, suggests that the damage will certainly continue and probably worsen. We reporters can copy and paste the sentence “Insurance companies estimate the cost at x million pounds” into our laptops, adjusting only the “x”.

When you visit a flood scene, you also put two and two together. The stench and heart-wrenching piles of small, familiar possessions, all ruined, are the dominant impression; but with them comes the spirit of communities determined to get something done and impressively knowledgeable about the local causes of flooding: moorland run-off at Hebden Bridge or new housing in the floodplain south of Preston, even a specific, badly maintained pinch in a watercourse at Flimby on the Cumbrian coast north of Workington.

This community spirit, multiplied 150 times, powers the groups which make up the National Flood Forum. Yet only in July, its chair, Charles Tucker, surveyed the bleak landscape of 294 defence schemes abandoned or delayed by public spending cuts – including one due at Morpeth, which was flooded in 2008 and again this week – and accused the government of “wringing its hands while the waters rise”.

Wringing out the soaking landscape would make so much more sense: meeting the threat of further flooding with the resource of much-trumpeted localism, and a heaven-sent chance to trial some Keynesian public spending which is tempting politicians as the recession grinds on. Flood defences have an exceptional record in this regard: they are unsuited to private sector involvement, as the Green Investment Bank acknowledges by ruling them out because of the lack of revenue streams – something that helped Roosevelt ward off inevitable cries of “socialism”.

We don’t have to look back to Keynes or Tennessee to get the point. Hop on London’s Docklands Light Railway down to Woolwich Arsenal and spend a day at the Thames Barrier. This was conceived after the 1953 North Sea floods which cost more than 300 lives in the UK (imagine that happening again), approved in 1965, started building in 1974 and was opened by the Queen 10 years later. It cost nearly £2bn at today’s prices. And everyone loves it, quite apart from its role in protecting the capital.

Anyone looking for a form of public works which would be popular and involving, the source of many jobs and spread over the English regions with their growing resentment of “London neglect”, need look no further. Vince Cable cast about at the Liberal Democrat conference this week for ways of regaining political ground in the north of England. Here it is.