IS GLOBAL WARMING REAL AND CAUSED BY MAN'S ACTIVITIES?
The answer to the first part of the question is that it is now certain that global warming is real. The measurements have been repeatrd by several different grouos of people and all agree.
Is it caused by mankind's activities through the burning of fossil fuels? Here the answer is slightly less certain, but only just. The Intergovernmental Panel on Climate Change (IPCC) concluded that it is extremely likely that most of the warming is caused by our use of fossil fuels. Here they define "extremely likely" to mean 95% probable. This means that there is only a 1 in 20 chance that most of the warming is natural. The IPCC is a body set up by the United Nations. It assembles many hundreds of the foremost climate researchers of the World to assess all the published research and decide where there is agreement and what the uncertainties are.
The rise of 0.80C in the Earth's temperature over the last century may not sound much but the forecast is that if we carry on burning fossil fuels at our present rate, we could see the World's average temperature up to 50C higher by the year 2100. Again, this doesn't sound a lot but to put it into perspective, the average Earth temperature rose by about 80C after the last ice age 15,000 years ago. At that time Keswick was under a layer of ice several thousands of feet thick. So a warming of 50C could at some point lead to catastrophic consequences after 2100 when our great grandchildren will be middle aged. Are we being fare to leave them with a problem like this?
If you read much of the popular press they would have you believe that there is much disagreement among climate scientists: this is untrue. See for yourself by having a look at the recent "Summary for Policy Makers" in the "2013 Assessment Report" on the IPCC website.