Chairman of the Intergovernmental Panel on Climate Change (IPCC), Rajendra K. Pachauri, said it is time to listen to science and act on climate change before it is too late.
Speaking at the opening ceremony of the United Nations Climate Summit in New York, Pachauri said it comes down to a matter of choice. "We can continue along our existing path and face dire consequences or act," he said.
"I couldn't stand before you if the threats of climate change had no solutions. But they do. We already have the means to build a better, more sustainable world.
"The solutions are many and while some solutions need additional development many are already available."
Renewable energy is a real option, Pachauri said. "Half of the world's new electricity generating capacity in 2012 came from renewables. And we can further reduce emissions by stopping deforestation," he said.
"We are told that limiting climate change will be too expensive. It will not. But wait until you get the bill for inaction. There are costs of taking action but they are nothing compared to the cost of inaction."
Pachauri released the IPCC's Fifth Assessment Report which is compiled by hundreds of scientists and is the most comprehensive assessment of climate change ever undertaken.
He said there is abundant evidence proving that "we are changing our climate."
"The oceans and atmosphere have warmed, the amounts of snow and ice have diminished, and the sea level has risen," Pachauri explained.
"Each of the last three decades has been successively warmer at the Earth's surface than any preceding decade since 1850. Greenhouse gases in our atmosphere have increased to levels unprecedented in the past 800,000 years."
Pachauri said the time to take action is running out. "If we want a chance to limit the global rise in temperature to two degrees Celsius, our emissions should peak by 2020. If we carry on business as usual, our opportunity
to remain below the two degree limit will slip away well before the middle of the century," he said.
