Query: ‘If we do nothing to reduce our greenhouse gas emissions, the kind of extreme heat we saw this past summer will be the norm when my young son is a grown man.’

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Scientific consensus on climate change <=SEP=> There is currently a strong scientific consensus that the Earth is warming and that this warming is mainly caused by human activities. This consensus is supported by various studies of scientists' opinions and by position statements of scientific organizations, many of which explicitly agree with the Intergovernmental Panel on Climate Change (IPCC) synthesis reports.  Nearly all actively publishing climate scientists (97–98%) support the consensus on anthropogenic climate change, and the remaining 2% of contrarian studies either cannot be replicated or contain errors.

Years of Living Dangerously <=SEP=> Years of Living Dangerously is an American documentary television series focusing on global warming . The first season , of nine weekly episodes , premiered in the US on April 13 , 2014 , on Showtime . It won an Emmy Award as Outstanding Documentary or Nonfiction Series . The second season , consisting of eight episodes , aired on the National Geographic Channel , beginning on October 30 , 2016 , with broader international distribution than the first season . Executive producers included James Cameron , Arnold Schwarzenegger , Robert Palumbo , and series creators Joel Bach and David Gelber ( formerly of 60 Minutes ) . Joseph Romm and Heidi Cullen were the chief science advisors .   The weekly episodes featured celebrity hosts with a history of environmental activism and well-known journalists with a background in environmental reportage . These `` correspondents '' traveled the world and throughout the U.S. to interview experts and ordinary people affected by , and seeking solutions to , the effects of global warming . They acted as reporters and proxies for the audience , asking questions to find out people 's opinions and to discover the scientific evidence . The final episode of season one featured an interview of President Barack Obama . Executive producers for season one were Cameron , Schwarzenegger , clean energy investor and environmental activist Daniel Abbasi , Jerry Weintraub , Bach and Gelber .   Episodes explored the effects of rising sea levels , historic droughts and flooding , water scarcity , ocean acidification , deforestation and the rapidly increasing extinction rate of species , but also focused on `` solutions that individuals , communities , companies and even governments can use to address worldwide climate change '' , including cheaper solar and wind energy , advancing battery technology and electric cars . Hosts included Cameron , Schwarzenegger , Harrison Ford , Ian Somerhalder , America Ferrera , David Letterman , Gisele Bündchen , Jack Black , Matt Damon , Jessica Alba , Sigourney Weaver , and various other actors and journalists .   Schwarzenegger reflected on how the series tries to make the issue of climate change resonate with the public : `` I think the environmental movement only can be successful if we are simple and clear and make it a human story . We will tell human stories in this project . The scientists would never get the kind of attention that someone in show business gets . '' Cameron elaborated : `` We did n't use our celebrities as talking head experts , because they 're not climate experts . They were concerned , intelligent , curious citizens who were out to find answers . They were functioning as journalists . '' Newsweek said that the celebrity hosts `` lend sparks to an issue that sends most viewers for the exits '' .

Carbon dioxide in Earth's atmosphere <=SEP=> Carbon dioxide is an important trace gas in Earth 's atmosphere . Currently it constitutes about 0.041 % ( equal to 410 parts per million ; ppm ) by volume of the atmosphere . Despite its relatively small concentration is a potent greenhouse gas and plays a vital role in regulating Earth 's surface temperature through radiative forcing and the greenhouse effect . Reconstructions show that concentrations of in the atmosphere have varied , ranging from as high as 7,000 ppm during the Cambrian period about 500 million years ago to as low as 180 ppm during the Quaternary glaciation of the last two million years .   Carbon dioxide is an integral part of the carbon cycle , a biogeochemical cycle in which carbon is exchanged between the Earth 's oceans , soil , rocks and the biosphere . Plants and other photoautotrophs use solar energy to produce carbohydrate from atmospheric carbon dioxide and water by photosynthesis . Almost all other organisms depend on carbohydrate derived from photosynthesis as their primary source of energy and carbon compounds .   The current episode of global warming is attributed to increasing emissions of and other greenhouse gases into Earth 's atmosphere . The global annual mean concentration of in the atmosphere has increased by more than 40 % since the start of the Industrial Revolution , from 280 ppm , the level it had for the last 10,000 years leading up to the mid-18th century , to 399 ppm as of 2015 . The present concentration is the highest in at least the past 800,000 years and likely the highest in the past 20 million years . The increase has been caused by anthropogenic sources , particularly the burning of fossil fuels and deforestation . The daily average concentration of atmospheric CO2 at Mauna Loa Observatory first exceeded 400 ppm on 10 May 2013 . It is currently rising at a rate of approximately 2 ppm/year and accelerating . An estimated 30 -- 40 % of the released by humans into the atmosphere dissolves into oceans , rivers and lakes , which contributes to ocean acidification .

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 .