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Highlights the importance of national enforcement against illegal trade in ensuring reductions in the emission of chemicals that damage the ozone layer and the climate system.

A report by the working group commissioned by the Pontifical Academy of Sciences.

Annual greenhouse gases emissions in 2010 were at their highest recorded level in spite of a global recession. The risk is growing that the climate system could pass tipping points that lead to abrupt and irreversible impacts on a continental scale, perhaps within decades. Successfully addressing climate change requires fast and aggressive action to reduce CO2 emissions, which are responsible for up to 55% of radiative forcing since 1750. It also requires fast and aggressive action to reduce emissions of the pollutants causing the other 45% of warming – the non-CO2 climate forcers, including hydrofluorocarbons (HFCs), black carbon, methane, and tropospheric ozone. Along with reducing CO2, reducing emissions of these non- CO2 climate forcers, which in most cases can be done using existing technologies and existing laws and institutions, can cut the rate of global warming in half for several decades and by two-thirds in the Arctic in the next 30 years. In addition, given the profoundly persistent nature of CO2, it is necessary to explore and implement “carbon-negative” strategies to drawdown existing CO2 on a timescale of decades rather than millennia, and ultimately produce a net drawdown of CO2 when sinks exceed sources.

There is growing international interest in mitigating climate change during the early part of this century by reducing emissions of short-lived climate pollutants (SLCPs), in addition to reducing emissions of CO2. The SLCPs include methane (CH4), black carbon aerosols (BC), tropospheric ozone (O3) and hydrofluorocarbons (HFCs). Recent studies have estimated that by mitigating emissions of CH4, BC, and O using available technologies, about 0.5 to 0.6◦C warming can be avoided by mid-21st century. Here we show that avoiding production and use of high-GWP (global warming potential) HFCs by using technologically feasible low-GWP substitutes to meet the increasing global demand can avoid as much as another 0.5◦C warming by the end of the century. This combined mitigation of SLCPs would cut the cumulative warming since 2005 by 50% at 2050 and by 60% at 2100 from the CO2-only mitigation scenarios, significantly reducing the rate of warming and lowering the probability of exceeding the 2◦C warming threshold during this century.

Stratospheric ozone, global warming, and the principle of unintended consequences—An ongoing science and policy success story.

This paper explores the business case for Indian AC companies to phase down HFCs and move to a future based on climate-friendly refrigerants and energy-efficient equipment designs.

Issue of Our Planet, the magazine of the United Nations Environment Programme.