Query: The past shows that climate change is normal, that warmer times and more atmospheric carbon dioxide have driven biodiversity and that cold times kill.”

Relevant passages:
Paleoclimatology <=SEP=> Paleoclimatology ( in British spelling , palaeoclimatology ) is the study of changes in climate taken on the scale of the entire history of Earth . It uses a variety of proxy methods from the Earth and life sciences to obtain data previously preserved within things such as rocks , sediments , ice sheets , tree rings , corals , shells and microfossils . It then uses the records to determine the past states of the Earth 's various climate regions and its atmospheric system . Studies of past changes in the environment and biodiversity often reflect on the current situation , specifically the impact of climate on mass extinctions and biotic recovery .

Biodiversity <=SEP=> Biodiversity a portmanteau of `` biological diversity , '' generally refers to the variety and variability of life on Earth . According to the United Nations Environment Programme , biodiversity typically measures variation at the genetic , the species , and the ecosystem level . Terrestrial biodiversity tends to be greater near the equator , which seems to be the result of the warm climate and high primary productivity . Biodiversity is not distributed evenly on Earth , and is richest in the tropics . These tropical forest ecosystems cover less than 10 per cent of earth 's surface , and contain about 90 percent of the world 's species . Marine biodiversity tends to be highest along coasts in the Western Pacific , where sea surface temperature is highest and in the mid-latitudinal band in all oceans . There are latitudinal gradients in species diversity . Biodiversity generally tends to cluster in hotspots , and has been increasing through time , but will be likely to slow in the future .   Rapid environmental changes typically cause mass extinctions . More than 99.9 percent of all species , amounting to over five billion species , that ever lived on Earth are estimated to be extinct . Estimates on the number of Earth 's current species range from 10 million to 14 million , of which about 1.2 million have been documented and over 86 percent have not yet been described . More recently , in May 2016 , scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described . The total amount of related DNA base pairs on Earth is estimated at 5.0 x 1037 and weighs 50 billion tonnes . In comparison , the total mass of the biosphere has been estimated to be as much as 4 TtC ( trillion tons of carbon ) . In July 2016 , scientists reported identifying a set of 355 genes from the Last Universal Common Ancestor ( LUCA ) of all organisms living on Earth .   The age of the Earth is about 4.54 billion years old . The earliest undisputed evidence of life on Earth dates at least from 3.5 billion years ago , during the Eoarchean Era after a geological crust started to solidify following the earlier molten Hadean Eon . There are microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia . Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old meta-sedimentary rocks discovered in Western Greenland . More recently , in 2015 , `` remains of biotic life '' were found in 4.1 billion-year-old rocks in Western Australia . According to one of the researchers , `` If life arose relatively quickly on Earth . . then it could be common in the universe . ''   Since life began on Earth , five major mass extinctions and several minor events have led to large and sudden drops in biodiversity . The Phanerozoic eon ( the last 540 million years ) marked a rapid growth in biodiversity via the Cambrian explosion -- a period during which the majority of multicellular phyla first appeared . The next 400 million years included repeated , massive biodiversity losses classified as mass extinction events . In the Carboniferous , rainforest collapse led to a great loss of plant and animal life . The Permian -- Triassic extinction event , 251 million years ago , was the worst ; vertebrate recovery took 30 million years . The most recent , the Cretaceous -- Paleogene extinction event , occurred 65 million years ago and has often attracted more attention than others because it resulted in the extinction of the dinosaurs .   The period since the emergence of humans has displayed an ongoing biodiversity reduction and an accompanying loss of genetic diversity . Named the Holocene extinction , the reduction is caused primarily by human impacts , particularly habitat destruction . Conversely , biodiversity impacts human health in a number of ways , both positively and negatively .   The United Nations designated 2011 -- 2020 as the United Nations Decade on Biodiversity .

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 .

Anoxic event <=SEP=> Oceanic anoxic events or anoxic events ( anoxia conditions ) refer to intervals in the Earth 's past where portions of oceans become depleted in oxygen ( O2 ) at depths over a large geographic area . During some of these events , euxinia , waters that contained hydrogen sulfide , developed . Although anoxic events have not happened for millions of years , the geological record shows that they happened many times in the past . Anoxic events coincided with several mass extinctions and may have contributed to them . These mass extinctions include some that geobiologists use as time markers in biostratigraphic dating . Many geologists believe oceanic anoxic events are strongly linked to slowing of ocean circulation , climatic warming , and elevated levels of greenhouse gases . Researchers have proposed enhanced volcanism ( the release of CO2 ) as the `` central external trigger for euxinia '' .

Effects of global warming on human health <=SEP=> The effects of global warming include effects on human health . The observed and projected increased frequency and severity of climate related impacts will further exacerbate the effects on human health . This article describes some of those effects on individuals and populations .