the 45% or 25% reduction goals to limit global warming to 1.5 °c or 2 °c, respectively. society denial and misinformation data has been cherry picked from short periods to falsely assert that global temperatures are not rising. blue trendlines show short periods that mask longer-term warming trends (red trendlines). blue dots show the so-called global warming hiatus. public debate about climate change has been strongly affected by climate change denial and misinformation, which originated in the united states and has since spread to other countries, particularly canada and australia. the actors behind climate change denial form a well-funded and relatively coordinated coalition of fossil fuel companies, industry groups, conservative think tanks, and contrarian scientists. like the tobacco industry, the main strategy of these groups has been to manufacture doubt about scientific data and results. many who deny, dismiss, or hold unwarranted doubt about the scientific consensus on anthropogenic climate change are labelled as "climate change skeptics", which several scientists have noted is a misnomer. there are different variants of climate denial: some deny that warming takes place at all, some acknowledge warming but attribute it to natural influences, and some minimise the negative impacts of climate change. manufacturing uncertainty about the science later developed into a manufactured controversy: creating the belief that there is significant uncertainty about climate change within the scientific community in order to delay policy changes. strategies to promote these ideas include criticism of scientific institutions, and questioning the motives of individual scientists. an echo chamber of climate-denying blogs and media has further fomented misunderstanding of climate change. public awareness and opinion the public substantially underestimates the degree of scientific consensus that humans are causing climate change. studies from 2019 to 2021 found scientific consensus to range from 98.7 to 100%. climate change came to international public attention in the late 1980s. due to media coverage in the early 1990s, people often confused climate change with other environmental issues like ozone depletion. in popular culture, the climate fiction movie the day after tomorrow (2004) and the al gore documentary an inconvenient truth (2006) focused on climate change. significant regional, gender, age and political differences exist in both public concern for, and understanding of, climate change. more highly educated people, and in some countries, women and younger people, were more likely to see climate change as a serious threat. partisan gaps also exist in many countries, and countries with high co2 emissions tend to be less concerned. views on causes of climate change vary widely between countries. concern has increased over time, to the point where in 2021 a majority of citizens in many countries express a high level of worry about climate change, or view it as a global emergency. higher levels of worry are associated with stronger public support for policies that address climate change. climate movement climate protests demand that political leaders take action to prevent climate change. they can take the form of public demonstrations, fossil fuel divestment, lawsuits and other activities. prominent demonstrations include the school strike for climate. in this initiative, young people across the globe have been protesting since 2018 by skipping school on fridays, inspired by swedish teenager greta thunberg. mass civil disobedience actions by groups like extinction rebellion have protested by disrupting roads and public transport. litigation is increasingly used as a tool to strengthen climate action from public institutions and companies. activists also initiate lawsuits which target governments and demand that they take ambitious action or enforce existing laws on climate change. lawsuits against fossil-fuel companies generally seek compensation for loss and damage. history early discoveries this 1912 article succinctly describes the greenhouse effect, how burning coal creates carbon dioxide to cause global warming and climate change. scientists in the 19th century such as alexander von humboldt began to foresee the effects of climate change. in the 1820s, joseph fourier proposed the greenhouse effect to explain why earth's temperature was higher than the sun's energy alone could explain. earth's atmosphere is transparent to sunlight, so sunlight reaches the surface where it is converted to heat. however, the atmosphere is not transparent to heat radiating from the surface, and captures some of that heat, which in turn warms the planet. in 1856 eunice newton foote demonstrated that the warming effect of the sun is greater for air with water vapour than for dry air, and that the effect is even greater with carbon dioxide (co2). she concluded that "an atmosphere of that gas would give to our earth a high temperature..." starting in 1859, john tyndall established that nitrogen and oxygen—together totaling 99% of dry air—are transparent to radiated heat. however, water vapour and gases such as methane and carbon dioxide absorb radiated heat and re-radiate that heat into the atmosphere. tyndall proposed that changes in the concentrations of these gases may have caused climatic changes in the past, including ice ages. svante arrhenius noted that water vapour in air continuously varied, but the co2 concentration in air was influenced by long-term geological processes. warming from increased co2 levels would increase the amount of water vapour, amplifying warming in a positive feedback loop. in 1896, he published the first climate model of its kind, projecting that halving co2 levels could have produced a drop in temperature initiating an ice age. arrhenius calculated the temperature increase expected from doubling co2 to be around 5–6 °c. other scientists were initially skeptical and believed that the greenhouse effect was saturated so that adding more co2 would make no difference, and that the climate would be self-regulating. beginning in 1938, guy stewart callendar published evidence that climate was warming and co2 levels were rising, but his calculations met the same objections. development of a scientific consensus in the 1950s, gilbert plass created a detailed computer model that included different atmospheric layers and the infrared spectrum. this model predicted that increasing co2 levels would cause warming. around the same time, hans suess found evidence that co2 levels had been rising, and roger revelle showed that the oceans would not absorb the increase. the two scientists subsequently helped charles keeling to begin a record of continued increase, which has been termed the "keeling curve". scientists alerted the public, and the dangers were highlighted at james hansen's 1988 congressional testimony. the intergovernmental panel on climate change (ipcc), set up in 1988 to provide formal advice to the world's governments, spurred interdisciplinary research. as part of the ipcc reports, scientists assess the scientific discussion that takes place in peer-reviewed journal articles. there is a near-complete scientific consensus that the climate is warming and that this is caused by human activities. as of 2019, agreement in recent literature reached over 99%. no scientific body of national or international standing disagrees with this view. consensus has further developed that some form of action should be taken to protect people against the impacts of climate change. national science academies have called on world leaders to cut global emissions. the 2021 ipcc assessment report stated that it is "unequivocal" that climate change is caused by humans.