While some people in the UK may have ‘enjoyed’ warmer summers over recent years, climate change is causing more extreme weather events and all kinds of problems from floods and moor fires to heat stroke and droughts.
Our Climatic Research Unit plays a lead role in the production of the important HadCRUT4 dataset. The annual global temperature figures for 2019 from this dataset confirm that the past decade was the warmest on record.
We know that the Earth is warming up. Our Climatic Research Unit proved this by studying our past and current climate. But the only way to measure how much global temperatures are rising is by recording and collating data from all around the world.
To estimate global temperature, scientists at our Climatic Research Unit, the Met Office Hadley Centre and the UK National Centre for Atmospheric Science come together to produce the HadCRUT4 dataset. This is compiled from millions of air and sea surface temperature measurements taken across the globe, from all continents and all oceans.
The annual global temperature figures for 2019 confirm that the past decade was the warmest on record. The data also show that the past five years were the warmest in the 170-year series.
The HadCRUT4 global temperature series shows that the average for 2019 as a whole was 1.05±0.1°C above pre-industrial levels, taken as the average over the period 1850-1900. 2019 is nominally the third warmest year in the HadCRUT4 series.However, the balance of evidence using multiple data sets suggests that 2019, a year without a strong El Niño, is the second warmest year for annual global temperatures since records began in 1850. Only 2016 has been warmer, a year when temperature was boosted by a significant El Niño.
NASA and NOAA have also published their global mean temperature estimates for 2019. All three datasets (NASA, NOAA and HadCRUT4) agree that the last five years were the warmest five years since each global record began. NASA and NOAA have 2019 as the second warmest year in their records.
Evidence from these three records, together with other estimates from reanalyses, suggests that 2019 was most likely the second warmest year. The differences between the various estimates arise largely from the way that the data-sparse polar regions are handled.
Why is the world warming up?
Humankind is the main contributor to global warming, increasing greenhouse gases in the atmosphere over the last 170 years. The effects of human-induced climate change are not limited to the surface temperature of our planet. Indicators across the land, atmosphere, oceans and ice show that our climate system is changing holistically and beyond what we would expect from natural variability.
Each decade from the 1980s onwards has been successively warmer than all the decades that came before. Regional variations in temperature help us to understand the mechanisms that cause warming in response to the build-up of greenhouse gases in the atmosphere.
Professor Tim Osborn
Tim is the Director of Research at our Climatic Research Unit and a Professor of Climate Science in our School of Environmental Sciences. A world-leading climatologist, Tim plays a lead role in the creation of the HadCRUT4 dataset and was a Lead Author of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.
"While we know that human activities are causing the globe to warm, it’s important to measure this warming as accurately as possible. We’re confident that the world has warmed by about 1°C since the late nineteenth century because different methods of working out the global temperature give very similar results."