Rising global greenhouse gas emissions will cost more than $200bn a year to return to today’s level of emissions by 2030

That's light but as the joke says, it's a start.

From Finfacts Ireland:

The United Nations Framework Convention on Climate Change secretariat on Wednesday put forward in detail (5mb pdf report) how much it would cost to return emissions to today’s levels by 2030, which may not be be sufficient to avoid some of the adverse consequences of climate change.

Scientists say that annual greenhouse gas emissions must peak by 2015 to 2020 in order to avoid catastrophic consequences.

The UNFCCC found that about $148 billion of projected annual investment in the energy generation sector should be channelled to renewables, nuclear energy, hydropower and systems to capture and store carbon dioxide, in order to cut emissions to the desired level...MORE

And from the UN:

Note: General Assembly President Sheikha Haya announced that the climate change debate was made carbon-neutral by offsetting emissions from the air travel to bring experts to the meeting, as well as the entire carbon-dioxide emissions of the United Nations Headquarters during the event, through an investment in a biomass fuel project in Kenya. The fuel switch project supports the use of agricultural waste instead of traditional fossil fuels to power a crude palm oil refinery, thereby reducing greenhouse gas emissions and creating new economic opportunities for local farmers.