Television naturalist Sir David Attenborough has called for a "moral change" among energy consumers to cut waste and reduce pollution.
Sir David said global warming would definitely get worse
He told the Commons environment committee there was "no question" that global warming would worsen.
"What we can do is make the situation deteriorate less than it's going to."
Sir David said "a general moral view" that wasting energy was wrong - such as there had been over wasting food during the Second World War - was needed.
The government-commissioned Stern Review, published in October, said carbon emissions had already pushed up global temperatures by half a degree Celsius
If no action was taken on emissions, there was more than a 75% chance of global temperatures rising between two and three degrees Celsius over the next 50 years, it added.
Sir David, whose series include Life on Earth, The Blue Planet and Planet Earth, said: "I'm hopeful that there's a real change taking place in moral attitudes that it's not to do with saving pennies here and there but it's morally wrong to waste energy because we are putting at risk our grandchildren."
He added: "People do look at 4x4s in central London and curl a lip already."
Sir David also told MPs: "I grew up during the war and during the war it was a common view that wasting anything was wrong.
"It wasn't that we thought we were going to defeat Hitler by eating a lot of gristle in our meat but it was actually wrong not to eat our food."
There needed to be a similar "general moral view that wasting energy is wrong", Sir David added.
He said: "Everything we do goes up there and stays up there for 100 years, in terms of carbon dioxide.
"Therefore it doesn't matter whether it's a tiny bit or a big bit: it's in the general attitude to this."
Sir David told MPs he had had doubts about climate change until attending a lecture by a US expert which proved that recent climate change was man-made, rather than part of the cycle of nature.
Now, he added, he was sure there was "not only climate change but humanity is responsible for that".
Sir David said he had been struck by the melting of glaciers in the Arctic and Antarctic.
He added: "The big changes that we see are primarily to do with pollution.
"We can see perfectly clearly that there are movements and increases in distribution of animals coming from warmer parts of Europe."
Dave Reay, an environmental scientist from Edinburgh University, told the committee that if people were to move towards more environmentally friendly behaviour, the information available had to become "personal to them".
For instance, consumers had to be made aware which cars gave out the fewest carbon emissions and how much energy could be saved by turning televisions off at the plug - rather than leaving them on standby.
Dr Reay said: "It's making the message more personal: that's the key."