Yes the earth heats up and cools down in cycles, but over the last 100 years or so the atmosphere's co2 content and average temperature has shot up, way above what would have been caused by natural causes. This is agreed by almost all of the leading scientists on the subject. If we leave it to keep warming up, we will not just be enjoying nice warm temparatures, infact it will quite likely be the opposite;
The warmer it gets, the more of the polar icecaps melt. This releases vast amounts of fresh water into the oceans. This in turn is likely to stop the gulf stream flowing and would make the UK's temperatures plunge to that of other countriers of our lattitude; like Alaska!
The increase of water in the oceans would also cause huge amounts of flooding in low lying countries. A huge amount of the worlds population live in low lying areas, so this would cause huge humanitarian problems, likely to cost the taxpayer and industry billions.
The warmer weather is also likely to increase the amount of tropical storms places like the gulf of mexico see. This can already be seen in an increase of level 5 and 6 hurricanes over the last decade.
Maybe we can have an effect on the future, maybe we can't. But we all should be trying our hardest to reduce the effect. I certainly would be ashamed if in 50-100 years time there were far more people living in poverty and famine, more deforrestation, and generally a worse world due to things we can chance now.
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and leave peoples cars and luxury's alone 
