Query: When the internal variability is removed from the temperature record, what we find is nearly monotonic, accelerating warming throughout the 20th Century.

Relevant passages:
20th century <=SEP=> The 20th century was a century that began on   January 1 , 1901 and ended on December 31 , 2000 . It was the tenth and final century of the 2nd millennium . It is distinct from the century known as the 1900s which began on January 1 , 1900 , and ended on December 31 , 1999 .   The 20th century was dominated by a chain of events that heralded significant changes in world history as to redefine the era : World War I and World War II , nuclear power and space exploration , nationalism and decolonization , the Cold War and post-Cold War conflicts ; intergovernmental organizations and cultural homogenization through developments in emerging transportation and communications technology ; poverty reduction and world population growth , awareness of environmental degradation , ecological extinction ; and the birth of the Digital Revolution . It saw great advances in communication and medical technology that by the late 1980s allowed for near-instantaneous worldwide computer communication and genetic modification of life . The term `` short twentieth century '' was coined to represent the events from 1914 to 1991 .   Global total fertility rates , sea level rise and ecological collapses increased ; the resulting competition for land and dwindling resources accelerated deforestation , water depletion . and the mass extinction of half the world 's estimated nine million unique species and wildlife population ; consequences which are now being dealt with . It took all of human history up to 1804 for the world 's population to reach 1 billion ; world population reached an estimated 2 billion in 1927 ; by late 1999 , the global population reached 6 billion . Global literacy averaged 80 % ; global lifespan-averages exceeded 40 + years for the first time in history , with over half achieving 70 + years ( three decades longer than it was a century ago ) .

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 .

Temperature <=SEP=> A temperature is an objective comparative measurement of hot or cold . It is measured by a thermometer . Several scales and units exist for measuring temperature , the most common being Celsius ( denoted ° C ; formerly called centigrade ) , Fahrenheit ( denoted ° F ) , and , especially in science , Kelvin ( denoted K ) .   The coldest theoretical temperature is absolute zero , at which the thermal motion of atoms and molecules reaches its minimum -- classically , this would be a state of motionlessness , but quantum uncertainty dictates that the particles still possess a finite zero-point energy . Absolute zero is denoted as 0 K on the Kelvin scale , − 273.15 ° C on the Celsius scale , and − 459.67 ° F on the Fahrenheit scale .   The kinetic theory offers a valuable but limited account of the behavior of the materials of macroscopic bodies , especially of fluids . It indicates the absolute temperature as proportional to the average kinetic energy of the random microscopic motions of those of their constituent microscopic particles , such as electrons , atoms , and molecules , that move freely within the material .   Temperature is important in all fields of natural science including physics , geology , chemistry , atmospheric sciences , medicine and biology as well as most aspects of daily life .

Instrumental temperature record <=SEP=> The instrumental temperature record provides the temperature of Earth 's climate system from the historical network of in situ measurements of surface air temperatures and ocean surface temperatures . Data are collected at thousands of meteorological stations , buoys and ships around the globe . The longest-running temperature record is the Central England temperature data series , that starts in 1659 . The longest-running quasi-global record starts in 1850 . In recent decades more extensive sampling of ocean temperatures at various depths have begun allowing estimates of ocean heat content but these do not form part of the global surface temperature datasets .