Query: If the same eruptions had happened near the more recent end of the dataset, they could have pushed the overall trend into negative numbers, or a long-term cooling,’ Christy said.”

Relevant passages:
Global warming hiatus <=SEP=> A global warming hiatus , also sometimes referred to as a global warming pause or a global warming slowdown , is a period of relatively little change in globally averaged surface temperatures . In the current episode of global warming many such 15-year periods appear in the surface temperature record , along with robust evidence of the long-term warming trend ; climate is classically averaged over 30-year periods .   Publicity has surrounded claims of a global warming hiatus during the period 1998 -- 2013 . The exceptionally warm El Niño year of 1998 was an outlier from the continuing temperature trend , and so subsequent annual temperatures gave the appearance of a hiatus : by January 2006 , it appeared to some that global warming had stopped or paused . A 2009 study showed that decades without warming were not exceptional , and in 2011 a study showed that if allowances were made for known variability , the rising temperature trend continued unabated . There was increased public interest in 2013 in the run-up to publication of the IPCC Fifth Assessment Report , and despite concerns that a 15-year period was too short to determine a meaningful trend , the IPCC included a section on a hiatus , which it defined as a much smaller increasing linear trend over the 15 years from 1998 to 2012 , than over the 60 years from 1951 to 2012 . Various studies examined possible causes of the short-term slowdown . Even though the overall climate system has continued to accumulate energy due to Earth 's positive energy budget , the available temperature readings at the Earth 's surface indicate slower rates of increase in surface warming than in the prior decade . Since measurements at the top of the atmosphere show that Earth is receiving more energy than it is radiating back into space , the retained energy should be producing warming in the Earth 's climate system .   Research reported in July 2015 on an updated NOAA dataset casts doubt on the existence of a hiatus , and it finds no indication of a slowdown even in earlier years . Scientists working on other datasets welcomed this study , though they have expressed the view that the recent warming trend was less than in previous periods of the same length . Subsequently , a detailed study supports the conclusion that warming is continuing , but it also find there was less warming between 2001 and 2010 than climate models had predicted , and that this slowdown might be attributed to short-term variations in the Pacific decadal oscillation ( PDO ) , which was negative during that period . Another review finds `` no substantive evidence '' of a pause in global warming . A statistical study of global temperature data since 1970 concludes that the term ` hiatus ' or ` pause ' is not justified .   Independent of these discussions about data and measurements for earlier years , 2015 turned out to be much warmer than any of the earlier years , already before El Niño conditions started . The warmth of 2015 largely ended any remaining scientific credibility of claims that the supposed `` hiatus '' since 1998 had any significance for the long-term warming trend . In January 2017 , a study published in the journal Science Advances cast further doubt on the existence of a recent pause , with more evidence that ocean temperatures have been underestimated . An April 2017 study found the data consistent with a steady warming trend globally since the 1970s , with fluctuations within the expected range of short term variability .

Phanerozoic <=SEP=> The Phanerozoic Eon ( British English Phanærozoic ) is the current geologic eon in the geologic time scale , and the one during which abundant animal and plant life has existed . It covers million years to the present , and began with the Cambrian Period when diverse hard-shelled animals first appeared . Its name was derived from the Ancient Greek words φανερός ( phanerós ) and ζωή ( zōḗ ) , meaning visible life , since it was once believed that life began in the Cambrian , the first period of this eon . The time before the Phanerozoic , called the Precambrian supereon , is now divided into the Hadean , Archaean and Proterozoic eons .   The time span of the Phanerozoic starts with the rapid emergence of a number of animal phyla ; the evolution of those phyla into diverse forms ; the emergence and development of complex plants ; the evolution of fish ; the emergence of insects and tetrapods ; and the development of modern fauna . Land plant life appeared in the early Phanerozoic eon . During this time span , tectonic forces caused the continents to move and eventually collect into a single landmass known as Pangaea , which then separated into the current continental landmasses .

John Christy <=SEP=> John Raymond Christy is a climate scientist at the University of Alabama in Huntsville ( UAH ) whose chief interests are satellite remote sensing of global climate and global climate change . He is best known , jointly with Roy Spencer , for the first successful development of a satellite temperature record .

Global cooling <=SEP=> Global cooling was a conjecture during the 1970s of imminent cooling of the Earth 's surface and atmosphere culminating in a period of extensive glaciation . This hypothesis had little support in the scientific community , but gained temporary popular attention due to a combination of a slight downward trend of temperatures from the 1940s to the early 1970s and press reports that did not accurately reflect the full scope of the scientific climate literature , which showed a larger and faster-growing body of literature projecting future warming due to greenhouse gas emissions . The current scientific opinion on climate change is that the Earth has not durably cooled , but underwent global warming throughout the 20th century .

Satellite temperature measurements <=SEP=> The temperature of the atmosphere at various altitudes as well as sea and land surface temperatures can be inferred from satellite measurements . These measurements can be used to locate weather fronts , monitor the El Niño-Southern Oscillation , determine the strength of tropical cyclones , study urban heat islands and monitor the global climate . Wildfires , volcanos , and industrial hot spots can also be found via thermal imaging from weather satellites .   Weather satellites do not measure temperature directly . They measure radiances in various wavelength bands . Since 1978 microwave sounding units ( MSUs ) on National Oceanic and Atmospheric Administration polar orbiting satellites have measured the intensity of upwelling microwave radiation from atmospheric oxygen , which is related to the temperature of broad vertical layers of the atmosphere . Measurements of infrared radiation pertaining to sea surface temperature have been collected since 1967 .   Satellite datasets show that over the past four decades the troposphere has warmed and the stratosphere has cooled . Both of these trends are consistent with the influence of increasing atmospheric concentrations of greenhouse gases .