You'd think a calamitous, life-threatening issue would be easy to spot. But it isn't always the case.

When the world teetered on the brink of nuclear war during the Cuban Missile Crisis, the gravity of the situation wasn't even grasped by those at the heart of it. "We came very, very close" former Secretary of Defense Robert McNamara told The Observer, "closer than we knew at the time."

Less than a year before the start of the bloodiest conflict in history – The Second World War – British Prime Minister Neville Chamberlain was hailing "peace in our time." He'd agreed a deal with Hitler in Munich. Not only was he catastrophically wrong, many across Europe, the UK and America agreed with his approach and he was hailed as the "saviour of modern Europe." History judges him differently now.

We stand on the precipice of another disaster. And yet, like Europeans in the 1930s going about our lives as if nothing was under threat, we ignore the existential crisis that is before us.

Make no mistake, this is an existential crisis, and if you think that terminology is over the top, maybe scaremongering, then you simply haven't grasped the level of the problem. The problem is, of course, climate change.

There are three reasons why we are yet to even acknowledge, let alone tackle climate change.

The first is vested interests. Too many companies stand to gain far too much money by their investment in fossil fuels.

The second is a more psychological issue. Because the problem is so vast and tackling it will require such monumental effort, we're suffering from Willful Ignorance. This phenomenon has been studied by psychologists. Broadly speaking, our biases and our comfort zones make it difficult to see the problem. "When we are blind to the flaws and failings of what we love [our lives as they are], we aren't effective either" argues one expert.

Thirdly, and this is difficult to hear, we can't even begin to tackle climate change because we are selfish. We in the rich West aren't yet directly affected by climate change so it is down our priority list. More perniciously, we aren't willing to give up our carbon guzzling habits for the good of those who already are suffering.

These three factors lead us to the place where one economist says we are already in dire straits. "Climate change is exacerbating more risks than ever before in terms of water crises, food shortages, constrained economic growth, weaker societal cohesion and increased security risks," says Cecilia Reyes.

So, what must be done?

This week a Christian activist Bill McKibben wrote a piece, which outlines how we need to behave. He says we have to put ourselves on a war footing. We must act as if climate change is the equivalent to the threat posed by the Nazis.

"This is no metaphor," he argues, "It's not that that global warming is like a world war. It is a world war. Its first victims, ironically, are those who have done the least to cause the crisis. But it's a world war aimed at us all."

Strong words, maybe. But is McKibben going overboard? No. He's a prophet – telling us what we need to hear. "The question is not, are we in a world war?" says McKibben, "the question is, will we fight back?"

What might this fight back look like? Well, McKibben has his own ideas, but let's deal with the three areas identified above.

Firstly we must tackle those corporate interests which rapaciously extract fossil fuels. It makes far more long-term sense to leave these fuels in the ground – we must persuade governments to legislate this.

Secondly, we have to open our eyes to the problems in front of us. Climate change is happening – don't put your head in the sand and let someone else worry about it. Read this Daily Mail report on how thousands of people are set to die in the UK and US as a result of extreme heat. Don't turn away. We have got the power to stop this.

Finally, our own selfishness. We rich westerners seem to feel we have the 'right' to fly wherever we like, whenever we like. We don't. Air travel is a major contributor to climate change. One round trip flight from coast to coast in the USA (or, to Europe) is the equivalent of a quarter of an average European's carbon emissions for the whole year.

While it might be nice to have a holiday in the sun, we simply can't carry on flying numerous times every year. We have to stop. Some business travel and some family-related flights could of course be continued. So it would be perfectly reasonable for a progressive flight tax to rise steeply after each flight you take – meaning one or two per year are possible but after that, they become very expensive.

We can also vastly cut our carbon emissions by eating no meat. How could you live without it? Well plenty of us do – it's possible. But if the thought of giving up altogether terrifies you – try cutting right back and only eating meat at the weekend. Remember – we're on a war footing here – rationing is normal.

"People in industrialized countries consume on average around twice as much meat as experts deem healthy," according to a report at The Scientific American. This isn't just liberal hand wringing – former Republican Governor of California Arnold Schwarzenegger says, "28% of the greenhouse gases come from eating meat and from raising cattle, so we can do a much better job."

Climate change is killing hundreds of thousands of people every year. Right now a thousand children die every day so that we can live our extravagant western lifestyles. If it continues unchecked, we will have unprecedented wars for water and other resources, vast migration crises and other as yet unknown calamities. There is already talk of this week's devastating floods in Louisiana being the result of climate change.

Some evangelical Christians deny that climate change is real or that it is a man-made phenomenon. This is despite an overwhelming scientific consensus. I worry that these Christians are at risk of one day being viewed in a similar light to Neville Chamberlain and the other appeasers, who limply sat by while the world was engulfed in chaos. They think they are doing the right thing, but ultimately, it will lead to disaster.

These Christians will decry this article as liberal propaganda. They'll say I'm letting my political agenda get in the way. They'll accuse me of being a leftist stooge who wants to stifle business. They say God wouldn't let the world burn up and that we will all be fine. But God has given us science to see what is happening and the knowledge to do something about it. Whether we choose to do so is up to us. Fortunately, many evangelicals are getting the message and acting – it's not too late, we can stop the world from burning.

So, it's time to suit up and go into battle on climate change. Let slip the dogs of war! It's our only choice.

Follow Andy Walton on Twitter @waltonandy