Summary of Global Climate Indicators 2018–2022

The flagship annual WMO State of Global Climate reports reports provide a summary of the state of global climate indicators, including global temperature, ocean heat and cryosphere indicators, such as sea ice and snow cover, among others. Each report includes input from National Meteorological and Hydrological Services, climate centres and experts around the world as well as from a wide range of UN partners. This chapter provides a brief summary of the key findings from the 2021 report and recent updates covering the 5-year period from 2018 to June 2022.

Global temperature

Figure 1. Five-year running average of global temperature anomalies (°C relative to 1850– 1900) from 1850–1854 to 2018–2022 (data to May or June 2022) shown as a difference from the 1850–1900 average. Six data sets are shown as indicated in the legend.

 

 

The years from 2015 to 2021 were the seven warmest on record. The 2018–2022 global mean temperature average (based on data up to May or June 2022) is estimated to be 1.17 ± 0.13 °C above the 1850–1900 average. This number is the average of six data sets¹, which individually have a range of 1.13 to 1.21 °C. It is the fourth warmest 5-year period on record according to all data sets surveyed (Figure 1), after 2016–2020, 2015–2019, and 2017–2021. Additionally, it is the warmest non-overlapping period, with the second being 2013–2017.

The recent, slightly lower, five-year average is associated with the switch from a strong El Niño present in 2015/2016 to persistent La Niña conditions that affected 2021 and the first half of 2022. El Niño gives a short-term boost to global temperatures, whereas years affected by La Niña are typically a little cooler.

The effect of the extended La Niña can be seen in the Pacific where surface temperatures were below the 1981–2010 period (Figure 2) in the eastern tropical Pacific, but warmer than average in the North Pacific and Southwest Pacific. Only a few areas of the world – parts of North America, the Southern Ocean and an area south of Greenland – were cooler than the recent average. However, most areas across the world were warmer than recent averages. Temperatures averaged over 2018–2022 were particularly high around Eurasia, large areas of Africa, Australia, and parts of South and Central America.

Figure 2. Five-year mean near-surface temperature difference from the 1981–2010 average for the period 2018–2022 (data to May or June 2022). Each map grid cell value is the median calculated from six data sets: HadCRUT5, GISTEMP, NOAAGlobalTemp, Berkeley Earth, JRA-55 and ERA5.

Ocean heat content

Most of the excess energy that accumulates in the Earth system due to increasing concentrations of GHGs is taken up by the ocean. This added energy warms the ocean and the consequent thermal expansion of the water leads to sea-level rise – to which melting land ice also contributes. The surface layers of the ocean have warmed more rapidly than the deeper waters, resulting in a rise in the global mean sea-surface temperature and an increase in the incidences of marine heatwaves.

Figure 3. Global ocean heat content 0-700 m from 1940 to May 2022 (Institute of Atmospheric Physics ocean analysis).

Around 90% of the accumulated heat in the Earth system is stored in the ocean, which is measured through Ocean Heat Content. Measurements of the layer from the surface to a 700 metre (m) depth show that the 2018–2022 global heat content (data to May 2022) was higher than in any previous year (Figure 3). The linear rate of change in the National Centers for Environmental Information (NCEI) “Levitus” data set in the years 2018–2022 is 0.8 x 1022 Joule/year. This corresponds to a heat flux in the 0–700 m layer of 0.7 Watts m^-2.

The upper 2 000 m depth of the ocean continued to warm in 2021 and it is expected that it will continue to do so in the future – a change which is irreversible on centennial to millennial timescales (Riser et al., 2016 and Roemmich et al., 2019).

All data sets agree that ocean warming rates show a particularly strong increase in the past two decades. Ocean warming rates for the 0–2 000 m depth layer (relative to the ocean surface) reached 1.0 (0.6) ± 0.1 W m^-2 over the period 2006–2021 (1971–2021). For comparison, the values for the upper 700 m depth amount to 0.7 (0.4) ± 0.1 W m^-2 over the period 2006–2021 (1971–2021). Below the 2 000 m depth, the ocean also warmed, albeit at a lower rate (Purkey et al., 2010) of 0.07 ± 0.04 W ^m-2.

Figure 4. Sea-ice extent differences from the 1981–2010 average in the Arctic (upper) and Antarctic (bottom) for the months with maximum ice cover (Arctic: March; Antarctic: September) and minimum ice cover (Arctic: September; Antarctic: February) from 1979 to March 2022 (US National Snow and Ice Data Center (NSIDC) and EUMETSAT Ocean and Sea Ice Satellite Application Facility (OSI-SAF)).

Cryosphere

Human influence is very likely the main driver of the decrease in Arctic sea-ice area between 1979–1988 and 2010–2019, which recorded decreases of about 40% in September and about 10% in March (IPCC, 2021). The current Arctic sea-ice cover (both annual and late summer) is at its lowest level since at least 1850 and is projected to reach practically ice-free conditions at its summer minimum at least once before 2050.

There has been no significant trend in Antarctic sea-ice area from 1979 to 2020 due to regionally opposing trends and large internal variability (IPCC, 2021). Antarctic sea-ice extent increased slowly from the start of the satellite era to around 2015, as can be seen in Figure 4. However, it dropped rapidly between 2015 and 2017, then returned close to the long-term average between 2017 and 2021 before reaching its lowest or second lowest minimum on record, according to different data sources from February 2022.

Glaciers are also highly sensitive to changes in temperature, precipitation, sunlight, and warming ocean waters, as well as other factors. Over the period 2000–2019, global glaciers and ice caps (excluding the Greenland and Antarctic ice sheets) experienced an average mass loss of 267 ± 16 gigatons (Gt) per year. Mass loss was higher, at 298 ± 24 Gt per year, in the later part of the period 2015–2019. However, glaciers in several mid-latitude regions thinned at more than double the global average (0.52 ± 0.03 m per year) from 2015 to 2019. Examples include thinning of 1.52 m per year in New Zealand, 1.24 m per year in Alaska, 1.11 m per year in Central Europe, and 1.05 m per year in Western North America (not including Alaska).

The World Glacier Monitoring Service collates and analyses global glacier mass balance data, including a set of 42 reference glaciers with long-term observations. For the glaciological year 2020/2021, preliminary data available from 32 of these reference glaciers indicate an average global mass balance of –0.77 m water equivalent (m w.e.)2. This is a smaller mass loss than the average for the last decade (–0.94 m w.e. from 2011 to 2020), but is larger than the average mass loss for the period 1991–2020, –0.66 m w.e.

2021 extreme events

Although understanding broad-scale changes in the climate is important, the acute impacts of weather and climate are most often felt during extreme meteorological events such as heavy rain and snow, droughts, heatwaves, cold waves, and storms, including tropical storms and cyclones. These can lead to or exacerbate other high-impact events such as flooding, landslides, wildfires and avalanches. This section highlights extreme weather events from 2021 and is based largely on input from WMO Members.

In 2021, exceptional heat waves affected western North America with record temperatures reaching 49.6 °C in British Columbia, Canada, breaking the previous Canadian national record by 4.6 °C. The extreme heat extended into the United States as well, which recorded its hottest summer on record averaged over the continental Untied States. Extreme heat also affected Central Europe and the broader Mediterranean region where Syracuse in Sicily, Italy, reached 48.8 °C. There were also numerous major wildfires during and after these heatwaves, from Canada to Siberia, where wildfires raged for the third successive year.

Western Europe experienced some of its most severe flooding on record in mid-July 2021. The worst-affected area was western Germany and eastern Belgium, where 100 to 150 mm of rain fell over a wide area on 14/15 July and Hagen (Germany) reported 241 mm of rainfall in 22 hours. Meanwhile, other parts of the world suffered from drought. In the Greater Horn of Africa, particularly Somalia, Kenya, and part of Ethiopia, drought developed during the course of the year after three successive below-average rainy seasons.

Abnormally cold conditions affected many parts of the central United States and northern Mexico in mid-February 2021. The most severe impacts were in Texas, which generally experienced its lowest temperatures since at least 1989. Additionally, the winter of 2020/2021 was particularly cold for many parts of Northern Asia. The Russian Federation had its coldest winter since 2009/2010 and below-average temperatures affected much of Japan in late December and early January. Much of China was also unusually cold during this period, with Beijing reaching −19.6 °C on 7 January 2021, its lowest temperature since 1966.

Footnotes

1 The six data sets are HadCRUT5 (2022 to May), GISTEMP, NOAAGlobalTemp, Berkeley Earth, ERA5 and JRA-55 (2022 to June).