Query: Those who contribute the least greenhouse gases will be most impacted by climate change.

Relevant passages:
Holocene extinction <=SEP=> The Holocene extinction , otherwise referred to as the Sixth extinction or Anthropocene extinction , is the ongoing extinction event of species during the present Holocene epoch , mainly due to human activity . The large number of extinctions spans numerous families of plants and animals , including mammals , birds , amphibians , reptiles and arthropods . With widespread degradation of highly biodiverse habitats such as coral reefs and rainforest , as well as other areas , the vast majority of these extinctions is thought to be undocumented . According to the species-area theory , and based on upper-bound estimating , the present rate of extinction may be up to 140,000 species per year , making it the greatest loss of biodiversity since the Cretaceous -- Paleogene extinction event .   The Holocene extinction includes the disappearance of large land animals known as megafauna , starting at the end of the last Ice Age . Megafauna outside of the African continent , which did not evolve alongside humans , proved highly sensitive to the introduction of new predation , and many died out shortly after early humans began spreading and hunting across the Earth ( additionally , many African species have also gone extinct in the Holocene ) . These extinctions , occurring near the Pleistocene -- Holocene boundary , are sometimes referred to as the Quaternary extinction event .   The arrival of humans on different continents coincides with megafaunal extinction . The most popular theory is that human overhunting of species added to existing stress conditions . Although there is debate regarding how much human predation affected their decline , certain population declines have been directly correlated with human activity , such as the extinction events of New Zealand and Hawaii . Aside from humans , climate change may have been a driving factor in the megafaunal extinctions , especially at the end of the Quaternary .   The ecology of humanity has been noted as being that of an unprecedented `` global superpredator '' that regularly preys on the adults of other apex predators and has worldwide effects on food webs . Extinctions of species have occurred on every land mass and ocean , with many famous examples within Africa , Asia , Europe , Australia , North and South America , and on smaller islands . Overall , the Holocene extinction can be characterized by the human impact on the environment . The Holocene extinction continues into the 21st century , with meat consumption , overfishing , ocean acidification and the amphibian crisis being a few broader examples of an almost universal , cosmopolitan decline in biodiversity . A ballooning human population along with profligate consumption are considered to be the primary drivers of this rapid decline .

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 .

Global warming <=SEP=> Global warming , also referred to as climate change , is the observed century-scale rise in the average temperature of the Earth 's climate system and its related effects . Multiple lines of scientific evidence show that the climate system is warming . Many of the observed changes since the 1950s are unprecedented in the instrumental temperature record which extends back to the mid 19th century , and in paleoclimate proxy records over thousands of years .   In 2013 , the Intergovernmental Panel on Climate Change ( IPCC ) Fifth Assessment Report concluded that `` It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century . '' The largest human influence has been emission of greenhouse gases such as carbon dioxide , methane and nitrous oxide . Climate model projections summarized in the report indicated that during the 21st century the global surface temperature is likely to rise a further 0.3 to for their lowest emissions scenario and 2.6 to for the highest emissions scenario . These findings have been recognized by the national science academies of the major industrialized nations and are not disputed by any scientific body of national or international standing .   Future climate change and associated impacts will differ from region to region around the globe . Anticipated effects include warming global temperature , rising sea levels , changing precipitation , and expansion of deserts in the subtropics . Warming is expected to be greater over land than over the oceans and greatest in the Arctic , with the continuing retreat of glaciers , permafrost and sea ice . Other likely changes include more frequent extreme weather events including heat waves , droughts , heavy rainfall with floods and heavy snowfall ; ocean acidification ; and species extinctions due to shifting temperature regimes . Effects significant to humans include the threat to food security from decreasing crop yields and the abandonment of populated areas due to rising sea levels . Because the climate system has a large `` inertia '' and greenhouse gases will stay in the atmosphere for a long time , many of these effects will not only exist for decades or centuries , but will persist for tens of thousands of years .   Possible societal responses to global warming include mitigation by emissions reduction , adaptation to its effects , building systems resilient to its effects , and possible future climate engineering . Most countries are parties to the United Nations Framework Convention on Climate Change ( UNFCCC ) ,  whose ultimate objective is to prevent dangerous anthropogenic climate change . Parties to the UNFCCC have agreed that deep cuts in emissions are required and that global warming should be limited to well below 2.0 C-change relative to pre-industrial levels , with efforts made to limit warming to 1.5 C-change .   Public reactions to global warming and concern about its effects are also increasing . A global 2015 Pew Research Center report showed a median of 54 % consider it `` a very serious problem '' . There are significant regional differences , with Americans and Chinese ( whose economies are responsible for the greatest annual CO2 emissions ) among the least concerned .