The United Nations has today (Thursday 16 September, 2021) published a synthesis report on the perils of climate change and the need for urgent climate action.

The report features hard-hitting forewords from both Antonio Guterres – Secretary-General of the United Nations – and Prof Peter Talaas – Secretary-General of the World Meteorological Organization.

The United in Science 2021 report draws heavily on the latest scientific evidence, including pivotal findings from the Met Office.

Professor Adam Scaife is one of the key Met Office contributors to the report. He said: “2021 is a vital year for climate change, as decision makers assemble in November in Glasgow for COP26. Everyone knows that many hopes are pinned on the final outcomes from the conference, but before decision makers can begin to agree meaningful action, it is vital for them to have access to the best-available climate data and predictions.”

The Met Office’s contribution to the report has concentrated on two principal areas: monitoring of global temperature and sea ice; and narrowing the uncertainty about what will happen to the climate in the next few years.

Adam Scaife continued: “The earth’s temperature is continuing to rise and as decision makers continue to decide on future policies to avert the worst outcomes of climate change and stay on a pathway within Paris Agreement limits, they require the best scientific information available.”

In an attempt to understand more about the latest global temperature rises and what will happen over the next five years, Met Office scientists continue to develop capacity in the science of observing and predicting variations in our climate.

For predicting climate in the near term, the Met Office Hadley Centre leads the World Meteorological Organisation’s effort to combine multiyear predictions from the best computer models available. Professor Scaife said: “This synthesis report takes the very latest observations and predictions and gives a stark warning that temporary exceedance of the 1.5°C level is quite possible in the next few years and that unless there are immediate, rapid and large-scale reductions in greenhouse gas emissions, limiting long-term warming to 1.5°C will be impossible.”

In December 2020, the Met Office and the University of East Anglia Climate Research Unit announced a series of key improvements to their long-running global temperature data set, HadCRUT, which contains data stretching back to 1850.

HadCRUT brings together measurements of near-surface air temperature made at weather stations around the world with measurements of the temperature of the top-most layer of the ocean (or sea-surface temperature). The updates to HadCRUT (now known as HadCRUT5) include:

• updated adjustments to handle the changing biases between different ways of measuring sea-surface temperatures over time;
• A significant increase in the number of weather stations used over land;
• Using statistical methods to extend the data set’s coverage in the early record and in areas that are still data-sparse today, including the rapidly warming Arctic. This provides more accurate estimates of global, hemispheric and regional temperature changes.

John Kennedy of the Met Office Hadley Centre said: “These revisions show slightly more warming in recent times, compared with previous iterations of the data set. The new data set provides decision makers with our best estimate yet of the rate of warming and its uncertainty and also serves as a reminder that the world has warmed considerably since 1850.”

The United in Science 2021 report, the third in a series, is coordinated by the World Meteorological Organization (WMO), with input from the UN Environment Programme (UNEP), the World Health Organization (WHO), the Intergovernmental Panel on Climate Change (IPCC), the Global Carbon Project (GCP), the World Climate Research Programme (WCRP) and the Met Office (UK).

The United in Science report provides details on:

• Greenhouse Gas Concentrations in the Atmosphere (WMO)
• Global greenhouse gas emissions and budgets (Global Carbon Project)
• Emissions Gap (UN Environment Programme)
• Global Climate in 2017-2021 and 2021-2025 (WMO, UK Met Office)
• Highlights of the Intergovernmental Panel on Climate Change Sixth Assessment Report – the Physical Science basis
• Sea level rise and coastal impacts (World Climate Research Programme)
• Heatwaves, widlfires and air pollution (World Health Organization/WMO)