Record levels of carbon dioxide in the atmosphere must prompt governments to take global warming more seriously, United Nations climate chief Christiana Figueres warns.
Last week the Mauna Loa observatory reported levels of the main greenhouse gas were now at 400 parts per million (ppm), its highest level for 3 million years, scientists say.
“With 400ppm CO2 in the atmosphere, we have crossed an historic threshold and entered a new danger zone,” Figueres said.
“The world must wake up and take note of what this means for human security, human welfare and economic development. In the face of clear and present danger, we need a policy response which truly rises to the challenge.
“We still have a chance to stave off the worst effects of climate change, but this will require a greatly stepped-up response across all three central pillars of action: action by the international community, by government at all levels, and by business and finance.”
Figueres is tasked with guiding governments towards a universal agreement on how to address climate change by 2015. An international review of climate science will be published later this year.
The Intergovernmental Panel on Climate Change(IPCC) is expected to warn urgent action must be taken to prevent the world warming beyond 2°C above pre-industrial levels, a target countries have previously agreed to avoid.
Temperatures above this level could have a variety of impacts, from the melting of the Greenland Ice Sheet causing rapid sea level rise, increased levels of desertification and more extreme weather events around the world.
Climate negotiations run by the UN have failed to prevent marked rises in greenhouse gas emissions in the past two decades.
In 2009 hopes of a landmark global deal on reducing emissions were dashed, but in 2011 countries agreed to try and build a collective agreement by 2015.
While progress is slow, the last meeting two weeks ago in Bonn offered an insight into what a legally binding climate deal could look like, providing a series of milestones and options for the process over the next two years.
Rules to measure climate ambition could also be agreed at a UN summit set to take place in Warsaw at the end of 2013, a step that would end years of debate over who is responsible for pollution in the atmosphere.
A new agreement between China and the USA to run a climate working group, sharing best practice and policy options, has also been greeted as a sign major economies are willing to increase their ambition.
The two countries are jointly responsible for over 42% of greenhouse gas emissions.
This weekend leading UK economist and climate change expert Lord Nick Stern warned that millions of people could be made homeless as a result of global warming.
Stern, who is head of the Grantham Research Institute on Climate Change, told the Observer newspaper temperatures could continue to rise to 5°C due to soaring levels of carbon dioxide in the atmosphere.
“When temperatures rise to that level, we will have disrupted weather patterns and spreading deserts,” he said.
“Hundreds of millions of people will be forced to leave their homelands because their crops and animals will have died. The trouble will come when they try to migrate into new lands, however. That will bring them into armed conflict with people already living there. Nor will it be an occasional occurrence. It could become a permanent feature of life on Earth.”