Atmospheric CO2 has risen above 400 parts per million and is accelerating. The Arctic Ocean may well be ice-free this summer; methane gas is being released from the melting permafrost into the atmosphere and ocean acidification is intensifying. Sea levels are now rising far faster than predicted only a couple of years ago.

All these changes are irreversible. They make maintaining the global temperature rise below 2C an illusory goal. The unavoidable outcome of this nightmare scenario is a rapidly deteriorating climatic situation.

It will pose a number of grave problems for all aspects of society in the short-term and certainly well before the end of the next parliament.

The effects will be economic as well as ecological and are already evident. The mitigation actions needed are colossal. They will drive up energy demand at a time when international agreements on climate change will require the imposition of strict limits on carbon emissions and drive up public expenditure as tax receipts from economic growth shrink.

The future of all nations is irrevocably and immediately threatened. Yet we see little or no discussion of this by any of the main political parties during this general election campaign.

We therefore request for the benefit of the electorate and as a matter of urgency that all parties specifically set down clearly what policies they propose on the following:

l ceasing all infrastructure development in flood risk areas as determined by the latest science and observations of ice- sheet collapse;

l plans to evacuate flood-prone cities and to protect critical infrastructure such as nuclear power stations;

l moving to a zero fossil-fuel economy by the next decade, with full acknowledgment of all the political and economic impacts;

l the extent of international co-operation to be pursued on climate change, in particular focusing on the management of security – given the paradox that the global nuclear weapon arsenal (including Trident) is being upgraded when the futures of all nations are most threatened by climate change.

Peter Wadhams

Professor of Ocean Physics, University of Cambridge

Angie Zelter

Dr Mark Levene

Dr Mayer Hillman

Robert Aldridge

Professor John Whitelegg

Dr Robin Stott

Jeffrey Newman

John Pilger

Paul Ingram

Kevin Lister

The present election campaign is being labelled fascinating by some and frustrating by others. My frustration is the comparative neglect of the massive issue of climate change.

A consensus of scientists suggests that on current trends we have 15 years before the emission of greenhouse gasses destabilises the world climate disastrously and irreversibly. With this prospect, political wrangling over many other issues becomes irrelevant or even absurd.

Why should political leaders not appeal to the electorate with a programme that involves the necessary investment in renewable energy sources and the disinvestment in fossil fuels?

The financial cost of such a policy would be substantial, but the long-term benefit would be immeasurable.

People do care about the future for their children and grandchildren. Rather than buy votes for short-term advantages, shouldn’t our leaders be visionaries who can harness this deeper concern, and implement effective policies on climate that can be replicated across the world?

Maurice Sinclair

Birmingham

The state of our democracy

Last night I attended a hustings for the local parliamentary candidates: Labour, Tory, Ukip and Green; no Lib Dem turned up.

Our young Labour candidate was by far the most impressive speaker, even agreeing at one point, against Labour policy, with the nice, inexperienced Green candidate. Our long-term Tory MP was just smug. The audience was packed with baying kippers.

The Ukip candidate started his address by regretting that people call them racists and then raged about those Asian men “grooming our girls” – such a problem in our town where there is barely one black face, except serving in the health service.

I have come to the conclusion that kippers are just lower-class Tories.

Carol Wilcox

Christchurch, Dorset

It seems odd that so many who voted for the Liberal Democrats at the last election should now be turning away from them on the grounds that some election promises had to be sacrificed in the interests of forming a coalition.

Surely the essence of the system of proportional representation to which the Lib Dems have for so long been devoted is that it almost always produces governments based upon compromise.

Perhaps Nick Clegg should remind his party that the gods punish us by giving us what we want.

R Rothschild

Lancaster

Why does everyone regard Nick Clegg’s commitment to oppose any increase in tuition fees as the worst broken promise in politics? And why are he and the Liberal Democrats so inept at explaining the failure?

No one doubts Clegg deeply regretted it when the dire economic situation and political weakness within the Coalition forced him, at lethal political cost, to renege on a promise.

Compare David Cameron’s promise before the election that he would not conduct a “top-down reorganisation of the NHS”. In power, there was no pressure forcing him to renege. He just did it because he wanted to.

Two broken promises: one regrettable but unavoidable; the other an unprincipled, cynical choice. After five years we don’t begin to understand coalition politics because we can’t be bothered to try.

Keith Farman

St Albans, Hertfordshire

If my constituency can be represented by a non-resident MP who in all likelihood would need a satnav to find it let alone get around it, may I suggest that voters be given the opportunity to cast their ballot in an area of their choosing?

This would avoid the repetitive debacle of the mass disenfranchisement of people whose vote is always wasted because some inept toff is parachuted into an ultra-safe seat (since they could not hope to contest a marginal) which the ghost of Jimmy Savile could probably win by wearing the right colour rosette.

This might be one step towards the much-needed change to proportional representation.

David Baxendale

Hinckley, Leicestershire

The fun way to avoid inheritance tax

Three correspondents (14 and 16 April) seem to believe that “doddery” old parents like me will be inhibited from downsizing our homes if the inheritance tax threshold is raised. They seem to imagine that we would be willing to impoverish ourselves by hanging on to underutilised and inconvenient homes. Their reasoning is flawed.

All assets, not just homes, are liable to inheritance tax. Whatever the threshold, downsizing alone will not increase that liability. In fact, downsizing may decrease it. You can blow all your cash profits on consumables, take a cruise or even gift it to your offspring and hope to avoid an early death – but don’t buy the Lamborghini as the tax man won’t believe you bought it as a hearse.

John Peacock

Rode, Somerset

My nightmare with Lariam

I find it beyond belief that after all these years of warnings, our Army is still providing Lariam as an anti-malarial to our troops!

Ten years ago I took Lariam for a short expedition into the Amazon. Never again! For months afterwards I was stricken by the most vivid and upsetting nightmares I have ever experienced. Some of these remain strongly in my memory all these years later.

I only had to do a little research on my return to discover that I was far from alone in having had terrible side effects from this drug. There’s no question: it should be banned forthwith.

Hallam Murray

London SW11

Austerity in the sixties

Simon Kelner (15 April) repeats the suggestion that it was difficult for a football pools winner to spend money in the early Sixties because there was very little to buy. Yes, life was tough before the invention of champagne, five-star hotels, cruises and air travel. No wonder the likes of Aristotle Onassis were obliged to lead such austere lives.

Gordon Elliot

Burford, Oxfordshire

Black oarswoman in the blue boat

Henry Harington bemoans the lack of black faces in the Boat Race crews last Saturday (letter, 15 April). Had he invested in HD television, he would have seen that the Cambridge Women’s No 7, Daphne Martschenko, is not only young, very gifted but also ... black!

Philip Stephenson

Cambridge