This graph does not prove that the Earth’s temperature today is the lowest it has been in 10,000 years.
There is now a scientific consensus that climate change is caused by human-caused greenhouse gas emissions. However, a graphic circulating on social media proves that global warming is not man-made, as the Earth was warmer thousands of years ago. That’s wrong: This graph shows ice core temperatures from Greenland, not global Earth temperatures over time, and the data goes back to the late 19th century—even before the onset of human-caused global warming in the last few decades. . It has now been established that the Earth has warmed particularly rapidly in recent years due to human emissions of greenhouse gases.
“Here is the temperature change in 9500 years…. Is it clear to anyone?“, asks the publication, which has been viewed nearly 80,000 times on Telegram since December 6, 2022, with a graph showing wide variations in temperature up to a 2.5 degree increase compared to the average value indicated by the curve red line.
“It was hotter in Jesus’ day than it is today“, adds a description of a Facebook post featuring the same visual. The latter also spread across Twitter (1, 2, 3), Facebook and blogs.
These publications show that the graph will show that global warming is not due to human activity, because temperatures may have been higher several thousand years ago than they are today.
Similar, viral claims were also shared on social media in English and German.
Screenshot on Telegram, taken on 01/26/2023
Facebook screenshot taken on 01/26/2023
The English title of the chart assures that “temperature anomalies“, i.e. temperature changes with respect to the base temperature calculated by taking average values,”From 7643 to the present“. The chart is from 2004 and “RB Alley“.
There are periods when the displayed temperature is higher than the temperature at the end of the chart. So the legend suggests that the current warming of the planet is very minimal compared to what happened in the past.
In fact, this graph and accompanying legend are misleading for several reasons.
First, it shows image data from an ice core (a cylinder of ice obtained by drilling vertically through the thickness of a glacier) taken in Greenland in the early 1990s, not the historical evolution of Earth’s temperature. So the curve shows the temperatures of central Greenland, not the entire Earth’s climate.as several climate experts explained to AFP.
Next, It says nothing about the current evolution of the climate since the years that stand on the x-axis (horizontal) in 1885. and no”today“, contrary to what social media posts indicate. Therefore, the graph does not show the recent rise in global temperatures, which is actually due to man-made greenhouse gas emissions.
Data from an ice core from Greenland
The graphic has actually been circulating the internet for several years and has already been shared with false headlines. Carbon Brief, a platform specializing in disinformation about climate change funded by the European Climate Fund, produced a fact-checking article on this graph in 2019.
The title bears the name of geologist and climatologist Richard B. Alley, a professor at Penn State University in Pennsylvania, USA, who works with the Intergovernmental Panel on Climate Change. (IPCC).
Richard Alley, contacted by AFP, showed on December 7, 2022 that the visual was actually using research published by other scientists.Journal of Geophysical Research: OceansIn 1997, the authors returned to the temperature history of Greenland.
To do this, researchers “Greenland Ice Sheet Project 2“(or GISP2), a drilling program carried out by American research institutes at the time, which made it possible to extract ice cores from the Greenland ice sheet, including a core more than 3,000 meters long, has now been completed. Greenland’s climate in the last 110,000 years.
The GISP2 core data has served as the basis for many subsequent studies, some of which have reconstructed temperatures in Greenland over the past 10,000 years ( here , there ). Richard Alley co-authored one of the seminal studies using GISP2 data published in 2004.
These data are analyzed by researchers of paleoclimatology, who study the climate of past times. they use what is said”climate archive“, contain ice sheets, but also tree trunk rings, stalagmites or sediments to obtain information about the climatic conditions of past times.
A French glaciologist operating an ice corer at the Franco-Italian Concordia station in central Antarctica (Archives / AFP)
Richard Alley also told AFP that he had received regular inquiries about the graphic for a decade. He gave a detailed answer to the allegations related to this chart, which he explained in detail in an opinion piece published on the magazine’s website.New York Times“In 2010.
He noted that “No individual temperature reading from any location can prove or disprove global warming, as this temperature is a local reading and one site does not represent the entire world“.
Bo Vinther, associate professor at the University of Copenhagen’s Niels Bohr Institute and lead author of a landmark 2009 study published in the journal Nature that reconstructed Greenland’s temperatures based on six different ice cores, also told AFP in December 2022, “it is not possible to draw firm conclusions about Greenland’s climate or Earth’s climate from these data“quoted in the chart.
The time arrow ends before the current temperature rise
The horizontal axis of the graph also shows dates ending in 1885, well before modern studies of current warming of the Earth’s climate.
Stefan Rahmstorf, a climatologist at the Potsdam Institute for Climate Impact Research (PIK), wrote on Twitter on November 20, 2022 that the currently released graph does not show the global average temperature and stopped before modern man-made processes began. Global Warming.
He also noted that “there are many variations“from confirmation delivered by”Climate deniers who don’t show global average temperatures (which is often Greenland) and even posit a paleoclimate curve that ends before modern warming“.
For paleoclimatologists and archaeologists, 1950 is considered the reference year. Thus, GISP2 data from 1950 “here“(“Here it is“where”P” in English). The latest GISP2 data is from 95 years ago (or “Before now“, “BP“in English) corresponds to 1855.
Noting the year 1885, we were unable to trace the source of the data presented in the chart. Richard Alley also noted that the origin of the latter was unclear, confirming to AFP that “here” corresponds to GISP2’s 1950, and the latest temperature data in the GISP2 data set is therefore 1855.
A study combining 73 historical temperature reconstructions from around the world in 2013 with recent measurement data shows a different curve than that presented in the currently shared papers.
It also appears that during certain millennia the Earth was warmer than it is now. But on the other hand, there is a sharp rise in temperature in recent decades.
Global temperature anomalies over the past 11,300 years relative to the historical average (1961-1990) (Marcott et al., Science 339 (2013), P. 1199)
Geologist Richard Alley also explained that the Earth’s temperature has indeed been higher for a long time than in the recent past. Therefore, large areas of the planet would be uninhabitable for humans due to high temperatures.
According to him, the CO2 already present in the atmosphere at that time was the driving factor of global warming. “The high temperatures of the past were mainly due to high levels of CO2. But they had natural causes and the warming was much slower than it is today. The current rise is not natural, it is caused by us“.
According to the researcher, the fact that there were large climate changes in the past without human intervention does not mean that humans cannot be responsible for the current climate change. Climate changes for many reasons, but mainly due to changes in the amount of CO2 in the atmosphere.
Global temperature increase in recent years
Indeed, Earth’s temperature has increased over the past 50 years at a rate and timescale not seen in 2,000 years, the IPCC notes in its sixth assessment report, published in April 2022. This paper constitutes the most comprehensive assessment of available scientific knowledge. climate change. According to him, the global average temperature will increase by 1.5 degrees in the next two decades.
The authors review hundreds of studies. The report concludes that there is evidence”revealed“Mankind is contributing to global warming by burning fossil fuels. The IPCC is based on the work of thousands of researchers around the world (including geologist Richard Alley, by the way).
Europe’s climate change program Copernicus (C3S) announced in early January that the period 2015-2022 was the eight hottest years on record globally, exceeding pre-industrial temperatures by more than one degree.
“About 1.2°C” warmer than the 1850-1900 average, 2022 confirms a global warming trend with exceptional droughts and floods, as well as further increases in greenhouse gas concentrations.“, highlights the annual report of this European program.
Temperature anomalies in 2022 compared to the 1981-2010 average (AFP / Simon MALFATTO, Paz PIZARRO, Sylvie HUSSON)
“Today, there is no longer any debate: there is 100% scientific consensus that humans are influencing the climate.“, Xavier Fettweis, a climatologist at the University of Liege, commented in a previous AFP review article.
Although the human origin of climate change is currently a consensus in the scientific community, the responsibility of humans in climate change is regularly questioned on social networks. AFP recently confirmed the false claims that the Sun is the main cause of global warming, that there is no link or consensus between CO2 emissions and global warming.
