Taking the Earth's Temperature
Global temperature data underpins international climate negotiations
Scientists at the Climatic Research Unit (CRU) research past climate history and its impact on humanity and the present day course and causes of climate change in order to help us understand the prospects for the future.
Observing the changing global temperature of Earth is crucial for demonstrating how much and how quickly the planet is warming. This data, together with scientific understanding of the causes of past and future warming, has underpinned the negotiation of international agreements to limit global warming to well below 2°C above pre-industrial levels.
CRU research has revealed changes to the world’s average temperature over the last 150 years. It is continually improved and updated, charting the warming as it reaches the 1 degree Celsius marker above the 1850-1900 period for the first time. The World Meteorological Organisation releases an annual update of the global temperature record, based on the combined work of UEA and other international research organisations, to coincide with each year’s UNFCCC climate talks.
The HadCRUT4 global temperature record compiled jointly by CRU and the Met Office has been central to all five Assessment Reports of the UN’s Intergovernmental Panel on Climate Change (IPCC) upon which successive rounds of international climate change negotiations have relied. Results from our research have appeared in the Summary for Policymakers of every IPCC report, from the first assessment in 1990, which led to the establishment of the United Nation’s Framework Convention on Climate Change (UNFCCC) through to the fifth assessment in 2013, which underpinned the 2015 Paris Agreement.
Most recently, the 2015 Paris agreement adopted the target of “holding the increase in the global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels.” Our HadCRUT4 global temperature record reveals that 2015, 2016 and 2017 were the three warmest years since records began – more than 150 years ago. Of these, 2015 and 2016 both received an extra boost from the El Niño phenomenon – an occasional, naturally-occurring warming of the tropical Pacific Ocean. The warmest year in the series that hasn’t been influenced by an El Niño was 2017. This confirms the urgent challenge ahead if the over-arching objectives of the Paris Agreement are to be met.
Prof Tim Osborn, director of UEA's Climatic Research Unit, said: “We estimate that the global average temperature for 2017 is around 1°C above pre-industrial levels, an increase almost entirely due to human activities – principally the release of carbon dioxide into the atmosphere by burning coal, oil and gas.”
“Average temperatures are important, but don’t tell us everything we need to know about climate change. Other CRU datasets allow users to look at finer-scale detail and also at other important variables such as precipitation.”
Prof Phil Jones, Professorial Fellow at the Climatic Research Unit
In 2014, scientists at UEA made the temperature dataset available via Google Earth. The new format allows users to scroll around the world, zoom in on six thousand weather stations and view monthly, seasonal and annual temperature data more easily than ever before.
Image: CRU temperature data set available via Google Earth.
It is important to place the instrumental record, which begins in 1850, in a longer context. To help in this the School of Environmental Sciences’ pioneering research in the area of climate reconstruction began in the 1970s in CRU, exploring evidence for climate change during historical time recorded in instrumental, natural and documentary proxy records.
More recent work in this area focusses on the use of high-resolution climate proxies, prominent among them being the analysis and interpretation of tree-ring data.
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