Query: HFCs (hydrofluorocarbons) are tens of thousands of times more polluting than carbon dioxide.

Relevant passages:
Kyoto Protocol <=SEP=> The Kyoto Protocol is an international treaty which extends the 1992 United Nations Framework Convention on Climate Change ( UNFCCC ) that commits State Parties to reduce greenhouse gas emissions , based on the fact that ( a ) global warming exists and ( b ) human-made CO2 emissions have caused it . The Kyoto Protocol was adopted in Kyoto , Japan , on 11 December 1997 and entered into force on 16 February 2005 . There are currently 192 parties ( Canada withdrew effective December 2012 ) to the Protocol .   The Kyoto Protocol implemented the objective of the UNFCCC to fight global warming by reducing greenhouse gas concentrations in the atmosphere to `` a level that would prevent dangerous anthropogenic interference with the climate system '' ( Art. 2 ) . The Protocol is based on the principle of common but differentiated responsibilities : it puts the obligation to reduce current emissions on developed countries on the basis that they are historically responsible for the current levels of greenhouse gases in the atmosphere .   The Protocol 's first commitment period started in 2008 and ended in 2012 . A second commitment period was agreed on in 2012 , known as the Doha Amendment to the protocol , in which 37 countries have binding targets : Australia , the European Union ( and its 28 member states ) , Belarus , Iceland , Kazakhstan , Liechtenstein , Norway , Switzerland , and Ukraine . Belarus , Kazakhstan and Ukraine have stated that they may withdraw from the Protocol or not put into legal force the Amendment with second round targets . Japan , New Zealand and Russia have participated in Kyoto 's first-round but have not taken on new targets in the second commitment period . Other developed countries without second-round targets are Canada ( which withdrew from the Kyoto Protocol in 2012 ) and the United States ( which has not ratified the Protocol ) . As of July 2016 , 66 states have accepted the Doha Amendment , while entry into force requires the acceptances of 144 states . Of the 37 countries with binding commitments , 7 have ratified .   Negotiations were held in the framework of the yearly UNFCCC Climate Change Conferences on measures to be taken after the second commitment period ends in 2020 . This resulted in the 2015 adoption of the Paris Agreement , which is a separate instrument under the UNFCCC rather than an amendment of the Kyoto protocol .

Greenhouse gas <=SEP=> A greenhouse gas ( abbrev . GHG ) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range . This process is the fundamental cause of the greenhouse effect . The primary greenhouse gases in Earth 's atmosphere are water vapor , carbon dioxide , methane , nitrous oxide , and ozone . Without greenhouse gases , the average temperature of Earth 's surface would be about -18 ° C , rather than the present average of 15 ° C . In the Solar System , the atmospheres of Venus , Mars and Titan also contain gases that cause a greenhouse effect .   Human activities since the beginning of the Industrial Revolution ( taken as the year 1750 ) have produced a 40 % increase in the atmospheric concentration of carbon dioxide , from 280 ppm in 1750 to 406 ppm in early 2017 . This increase has occurred despite the uptake of a large portion of the emissions by various natural `` sinks '' involved in the carbon cycle . Anthropogenic carbon dioxide emissions ( i.e. , emissions produced by human activities ) come from combustion of fossil fuels , principally coal , oil , and natural gas , along with deforestation , soil erosion and animal agriculture .   It has been estimated that if greenhouse gas emissions continue at the present rate , Earth 's surface temperature could exceed historical values as early as 2047 , with potentially harmful effects on ecosystems , biodiversity and the livelihoods of people worldwide . Recent estimates suggest that on the current emissions trajectory the Earth could pass a threshold of 2 ° C global warming , which the United Nations ' IPCC designated as the upper limit to avoid `` dangerous '' global warming , by 2036 .

Carbon offset <=SEP=> A carbon offset is a reduction in emissions of carbon dioxide or greenhouse gases made in order to compensate for or to offset an emission made elsewhere .   Carbon offsets are measured in metric tons of carbon dioxide-equivalent ( CO2e ) and may represent six primary categories of greenhouse gases : carbon dioxide , methane ( CH4 ) , nitrous oxide ( N2O ) , perfluorocarbons ( PFCs ) , hydrofluorocarbons ( HFCs ) , and sulfur hexafluoride ( SF6 ) . One carbon offset represents the reduction of one metric ton of carbon dioxide or its equivalent in other greenhouse gases .   There are two markets for carbon offsets . In the larger , compliance market , companies , governments , or other entities buy carbon offsets in order to comply with caps on the total amount of carbon dioxide they are allowed to emit . This market exists in order to achieve compliance with obligations of Annex 1 Parties under the Kyoto Protocol , and of liable entities under the EU Emission Trading Scheme . In 2006 , about $ 5.5 billion of carbon offsets were purchased in the compliance market , representing about 1.6 billion metric tons of CO2e reductions .   In the much smaller , voluntary market , individuals , companies , or governments purchase carbon offsets to mitigate their own greenhouse gas emissions from transportation , electricity use , and other sources . For example , an individual might purchase carbon offsets to compensate for the greenhouse gas emissions caused by personal air travel . Many companies ( see list ) offer carbon offsets as an up-sell during the sales process so that customers can mitigate the emissions related with their product or service purchase ( such as offsetting emissions related to a vacation flight , car rental , hotel stay , consumer good , etc. ) . In 2008 , about $ 705 million of carbon offsets were purchased in the voluntary market , representing about 123.4 million metric tons of CO2e reductions . Some fuel suppliers in the UK offer fuel which has been carbon offset such as Fuel dyes .   Offsets are typically achieved through financial support of projects that reduce the emission of greenhouse gases in the short - or long-term . The most common project type is renewable energy , such as wind farms , biomass energy , or hydroelectric dams . Others include energy efficiency projects , the destruction of industrial pollutants or agricultural byproducts , destruction of landfill methane , and forestry projects . Some of the most popular carbon offset projects from a corporate perspective are energy efficiency and wind turbine projects .   Carbon offsetting has gained some appeal and momentum mainly among consumers in western countries who have become aware and concerned about the potentially negative environmental effects of energy-intensive lifestyles and economies . The Kyoto Protocol has sanctioned offsets as a way for governments and private companies to earn carbon credits that can be traded on a marketplace . The protocol established the Clean Development Mechanism ( CDM ) , which validates and measures projects to ensure they produce authentic benefits and are genuinely `` additional '' activities that would not otherwise have been undertaken . Organizations that are unable to meet their emissions quota can offset their emissions by buying CDM-approved Certified Emissions Reductions . Emissions from burning fuel , such as red diesel , has pushed one UK fuel supplier to create a carbon offset fuel named Carbon Offset Red Diesel .   Offsets may be cheaper or more convenient alternatives to reducing one 's own fossil-fuel consumption . However , some critics object to carbon offsets , and question the benefits of certain types of offsets .  Due diligence is recommended to help businesses in the assessment and identification of `` good quality '' offsets to ensure offsetting provides the desired additional environmental benefits , and to avoid reputational risk associated with poor quality offsets .   Offsets are viewed as an important policy tool to maintain stable economies and to improve sustainability . One of the hidden dangers of climate change policy is unequal prices of carbon in the economy , which can cause economic collateral damage if production flows to regions or industries that have a lower price of carbon -- unless carbon can be purchased from that area , which offsets effectively permit , equalizing the price .

Montreal Protocol <=SEP=> The Montreal Protocol on Substances that Deplete the Ozone Layer ( a protocol to the Vienna Convention for the Protection of the Ozone Layer ) is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion . It was agreed on 16 September 1987 , and entered into force on 01 January 1989 , followed by a first meeting in Helsinki , May 1989 . Since then , it has undergone eight revisions , in 1990 ( London ) , 1991 ( Nairobi ) , 1992 ( Copenhagen ) , 1993 ( Bangkok ) , 1995 ( Vienna ) , 1997 ( Montreal ) , 1998 ( Australia ) , 1999 ( Beijing ) and 2016 ( Kigali , adopted , but not in force ) . As a result of the international agreement , the ozone hole in Antarctica is slowly recovering . Climate projections indicate that the ozone layer will return to 1980 levels between 2050 and 2070 . Due to its widespread adoption and implementation it has been hailed as an example of exceptional international co-operation , with Kofi Annan quoted as saying that `` perhaps the single most successful international agreement to date has been the Montreal Protocol '' . In comparison , effective burden sharing and solution proposals mitigating regional conflicts of interest have been among the success factors for the ozone depletion challenge , where global regulation based on the Kyoto Protocol has failed to do so . In this case of the ozone depletion challenge , there was global regulation already being installed before a scientific consensus was established . Also , overall public opinion was convinced of possible imminent risks .   The two ozone treaties have been ratified by 197 parties , which includes 196 states and the European Union , making them the first universally ratified treaties in United Nations history .   These truly universal treaties have also been remarkable in the expedience of the policy making process at the global scale , where only 14 years lapsed between a basic scientific research discovery ( 1973 ) and the international agreement signed ( 1985 & 1987 ) .

Hydrofluorocarbon <=SEP=> Hydrofluorocarbons ( HFCs ) , organic compounds that contain fluorine and hydrogen atoms , are the most common type of organofluorine compounds . They are commonly used in air conditioning and as refrigerants in place of the older chlorofluorocarbons such as R-12 and hydrochlorofluorocarbons such as R-21 . They do not harm the ozone layer as much as the compounds they replace ; however , they do contribute to global warming . Their atmospheric concentrations and contribution to anthropogenic greenhouse gas emissions are rapidly increasing , causing international concern about their radiative forcing .   Fluorocarbons with few C -- F bonds behave similarly to the parent hydrocarbons , but their reactivity can be altered significantly . For example , both uracil and 5-fluorouracil are colourless , high-melting crystalline solids , but the latter is a potent anti-cancer drug . The use of the C-F bond in pharmaceuticals is predicated on this altered reactivity . Several drugs and agrochemicals contain only one fluorine center or one trifluoromethyl group .   Unlike other greenhouse gases in the Paris Agreement , hydrofluorocarbons have other international negotiations .   In September 2016 , the so-called New York Declaration urged a global reduction in the use of HFCs . On 15 October 2016 , due to these chemicals ' contribution to climate change , negotiators from 197 nations meeting at the summit of the United Nations Environment Programme in Kigali , Rwanda reached a legally-binding accord to phase out hydrofluorocarbons ( HFCs ) in an amendment to the Montreal Protocol .