State of the climate: 2022 is currently tied for fourth warmest year on record

§ Fourth warmest year to date

While human emissions of CO2 and other greenhouse gases are responsible for all of the Earth’s long-term warming, temperatures in any given year are strongly influenced by short-term variations in the Earth’s climate that are typically associated with El Niño and La Niña events (collectively referred to as ENSO). 

These fluctuations in temperature between the ocean and atmosphere in the tropical Pacific help make some individual years warmer and some cooler. Global temperatures in 2022 have been moderately lowered by an unusual “triple dip” La Niña event, with cool conditions in the tropical Pacific pushing down global temperatures. 

In this latest quarterly state of the climate assessment, Carbon Brief analysed records from six different research groups that report global surface temperature records: NASA; NOAA; Met Office Hadley Centre/UEA; Berkeley Earth; Cowtan and Way; and Copernicus/ECMWF. 

The figure below shows how temperatures so far in 2022 (black line) compare to prior years (grey lines) in the NASA GISTEMP dataset. It shows the temperature of the year so far for each month of the year, from January through to the full annual average. In the NASA dataset, 2022 is tied for the fourth warmest year on record so far, cooler than three of the years in the past decade, but warmer than any other year since records began.

This year had a bit of a cooler start than many recent years, but warmer temperatures over the past few months have pushed year-to-date values upwards. However, with the “triple dip” La Niña event in the tropical Pacific, it remains to be seen what the final two months of the year will bring. (Final end-of-year data will not be published until January.)

The table below shows how each month in 2022 ranked across all the datasets examined –  with “3rd” indicating the third warmest temperature on record for that month occurred in 2022. Note that Hadley and Berkeley extend back to 1850, NASA and NOAA go back to 1880, and Copernicus/ECMWF is only available since 1979.

While the first five months of the year had relatively cool temperatures compared to the same months over the past decade, they were still between the fifth and ninth warmest since records began in the late 1800s. Summer months in 2022 were quite warm, with June in particular setting new all-time high temperature records for the month globally in two datasets (and clocking in as the second and third warmest on record in two others). Temperatures have remained relatively warm, with most datasets showing between the second and sixth warmest months on record.

The chart below compares the annual global surface temperatures from the five different groups since 1970. The coloured lines show the temperature for each year, while the dots on the right-hand side show the year-to-date estimate for January to October 2022.

Values are shown relative to a common baseline period – the 1981-2010 average temperature for each series – to more accurately compare them over the past few decades. Surface temperature records have shown around 0.9C warming since the year 1970, a warming rate of between 0.18C and 0.2C per decade, depending on the dataset.

While 2022 has been cooler than some of the past few years due to persistent La Niña conditions, these are expected to fade in early 2023. The figure below shows a range of different ENSO forecast models produced by different scientific groups. The values shown are sea surface temperature variations in the tropical Pacific – the El Niño 3.4 region – for three-month periods. The dynamical model average is shown in red, while that for statistical models is shown in green. The dotted lines represent the thresholds for La Niña (below 0.5C) or El Niño (above 0.5C) conditions.

§ Exceptional warmth in Europe and Asia

While global temperatures have increased rapidly over the past 50 years, looking at the global average only tells half the story. Warming has been faster over land – and much faster in the Arctic. 

So far, 2022 has seen exceptionally warm temperatures over many parts of the world. Nearly all of western Europe and large parts of China have seen their warmest January-October period ever recorded, as has Iran, Afghanistan, Pakistan, Nepal and the Antarctic Peninsula. In Pakistan, these record-warm temperatures have been accompanied by catastrophic flooding that affected more than 33 million people, destroyed 1.7m homes, and led to nearly 1,400 deaths.

Regions of the world setting all-time records for the year so far are shown in dark red in the figure below.

Almost everywhere on the planet saw warmer-than-usual temperatures for the year so far, with the exception of the tropical Pacific which has been cooled by persistent La Nina conditions. The global temperature anomalies (changes) relative to the 1951-80 period are shown in the map below. 

§ On track to be between the fourth and sixth warmest year

Using the data from the first 10 months of the year, plus both past and forecast future ENSO conditions, Carbon Brief has produced a prediction of where 2022 temperatures will most likely land for each different surface temperature record. 

The results are shown in the table below, with the probability of the year ending up as the fourth, fifth, sixth or seventh warmest on record shown for each dataset (there is virtually no chance that 2022 will end up above the fourth warmest or below the seventh warmest).

While all five datasets produce similar projections for 2022 annual temperatures, there are slight differences that result in different rankings. This year is most likely to be the sixth warmest on record in the Hadley HadCRUT5 dataset, the fifth warmest on record in the NASA GISTEMP dataset, the sixth warmest in NOAA, fifth warmest in Berkeley, and fifth warmest in Copernicus/ECMWF.

Back at the start of 2022 a number of groups, including Carbon Brief, estimated where 2022 annual temperatures might end up based on data through the end of 2021. The figure below shows the four different forecasts (from NASA’s Dr Gavin Schmidt, the UK Met Office, Berkeley Earth’s Dr Robert Rohde, and Carbon Brief), along with Carbon Brief’s latest projection for the NASA GISTEMP database using data through October 2022 (see the methodological note at the end for technical details about how these calculations were carried out).

While the final outcome for 2022 will be within the error bars of all the different estimates, it will likely be closest to that of Dr Robert Rohde, higher than those of the UK Met Office and Carbon Brief, and below that of Dr Gavin Schmidt.

§ Current temperature in-line with model projections

Climate models provide physics-based estimates of future warming given different assumptions about future emissions, greenhouse gas concentrations and other climate-influencing factors. 

The figure below shows the range of individual models forecasts featured in the Intergovernmental Panel on Climate Change’s (IPCC) fifth assessment report – known collectively as the CMIP5 models – between 1970 and 2030, with grey shading and the average projection across all the models shown in black. Individual observational temperature records are represented by coloured lines.

In these models, estimates of temperatures prior to 2005 are a “hindcast” using known past climate influences, while temperatures projected after 2005 are a “forecast” based on an estimate of how things might change.

While global temperatures were running a bit below the pace of warming projected by climate models between 2005 and 2014, the last decade has been pretty close to the model average. This is particularly true for globally complete temperature records, such as HadCRUT5, NASA, Berkeley Earth and the Copernicus/ECMWF reanalysis, which include temperature estimates for the whole Arctic.

§ Greenhouse gas concentrations reach record highs

Greenhouse gas concentrations reached a new high in 2022, driven by human emissions from fossil fuels, land-use change and agriculture. 

Three greenhouse gases – CO2, methane (CH4) and nitrous oxide (N2O) – are responsible for the bulk of additional heat trapped by human activities. CO2 is by far the largest factor, accounting for roughly 50% of the increase in “radiative forcing” since the year 1750. Methane accounts for 29%, while N2O accounts for around 5%. The remaining 16% comes from other factors including carbon monoxide, black carbon and halocarbons, such as CFCs.

Human emissions of greenhouse gases have increased atmospheric concentrations of CO2, methane and nitrous oxide to their highest levels in at least a few million years – if not longer. 

The figure below shows concentrations of these greenhouse gases – in parts per million (ppm) for CO2 and parts per billion (ppb) for methane and nitrous oxide – from the early 1980s through August 2022 (the most recent data currently available).

The atmospheric concentration of CH4 began to increase again in 2006 after a plateau from 1999. It further sped up since 2014, with roughly linear growth of 8ppb each year since. Unlike CO2 and N2O, CH4 has a relatively short atmospheric lifetime and does not accumulate in the atmosphere in the long term. This means that – to a first approximation – the level of CH4 in the atmosphere is directly proportional to the level of emissions over the past decade.

If emissions remain flat, atmospheric CH4 will be flat, while increasing emissions will show up as increased atmospheric CH4. If CO2 and N2O emissions remain flat, on the other hand, atmospheric concentrations would continue to increase.

While there are some complications around changes in the ability of the atmosphere to remove CH4 over time (through interactions with the OH molecule), the rise in methane concentrations in recent years strongly suggests that global emissions of CH4 have also been increasing.

§ Record-low Antarctic sea ice in much of 2022

Highly accurate observations of Arctic and Antarctic sea ice have been available since polar-observing satellites became available in the late 1970s. Arctic sea ice extent during the first two-thirds of 2022 has been at the low end of the historical 1979-2010 range, but only came close to setting a new record daily low in early March and mid-June. 

Antarctic sea ice, on the other hand, was at or near record lows for all of the first third of the year and the months of July and August. Late February saw the lowest Antarctic sea ice extent since records began, though the degree to which this was driven by climate change remains unclear given the lack of a clear long-term trend in the region – unlike in the Arctic, where sea ice declines are more clearly driven by warming. 

The figure below shows both Arctic and Antarctic sea ice extent in 2022 (solid red and blue lines), the historical range in the record between 1979 and 2010 (shaded areas) and the record lows (dotted black line). Unlike global temperature records (which only report monthly averages), sea ice data is collected and updated on a daily basis, allowing sea ice extent to be viewed through to the present day.

However, sea ice extent only tells part of the story. In addition to declining ice extent, the sea ice that remains tends to be younger and thinner than ice that used to cover the region. The figure below, using data from the Pan-Arctic Ice Ocean Modelling and Assimilation System (PIOMAS), shows the Arctic sea ice thickness for every year between 1979 and 2022 and highlights how it has declined. 

§ Methodological note

A statistical multivariate regression model was used to estimate the range of likely 2022 annual temperatures for each group that provides a temperature record. This model used the average temperature over the first 10 months of the year, the latest monthly temperature value (October 2022), the average ENSO 3.4 region value during the first 10 months of the year and the average predicted ENSO 3.4 value during the last two months of the year to estimate the annual temperatures. 

The model was trained on the relationship between these variables and annual temperatures over the period from 1950 through 2021 (or 1979 through 2021 for the Copernicus/ECMWF reanalysis dataset). The model then uses this fit to predict both the most likely 2022 annual value for each group, as well as the 95% confidence interval. The predicted ENSO 3.4 region values for the last two months of 2022 are taken from the NMME model mean forecast.

The percent likelihood of different year ranks for 2022 is estimated by using the output of the regression model, assuming a normal distribution of results. This allows Carbon Brief to estimate what percent of possible 2022 annual values fall above and below the temperatures of prior years for each group.