Berkeley Earth, a California-based non-profit research organization, has been preparing independent analyses of global mean temperature changes since 2013. The following is our report on global mean temperature during 2019.
We conclude that 2019 was the second warmest year on Earth since 1850. The global mean temperature in 2019 was colder than 2016, but warmer than every other year that has been directly measured. Consequently, 2016 remains the warmest year in the period of historical observations. Year-to-year rankings are likely to reflect short-term natural variability, but the overall pattern remains consistent with a long-term trend towards global warming.
Annual Temperature Anomaly
|Relative to 1981-2010 Average||Relative to 1951-1980 Average|
|Year||Rank||Anomaly in Degrees Celsius||Anomaly in Degrees Fahrenheit||Anomaly in Degrees Celsius||Anomaly in Degrees Fahrenheit|
|2019||2||0.54 ± 0.05||0.96 ± 0.08||0.90 ± 0.05||1.62 ± 0.08|
|2018||5||0.40 ± 0.05||0.72 ± 0.08||0.77 ± 0.05||1.38 ± 0.08|
|2017||3||0.47 ± 0.05||0.84 ± 0.08||0.84 ± 0.05||1.51 ± 0.08|
|2016||1||0.58 ± 0.04||1.05 ± 0.08||0.95 ± 0.04||1.71 ± 0.08|
|2015||4||0.45 ± 0.05||0.80 ± 0.08||0.81 ± 0.05||1.46 ± 0.08|
|2014||7||0.31 ± 0.05||0.55 ± 0.08||0.67 ± 0.05||1.21 ± 0.08|
|2013||11||0.24 ± 0.05||0.44 ± 0.08||0.61 ± 0.05||1.10 ± 0.08|
|2012||15||0.22 ± 0.04||0.39 ± 0.08||0.59 ± 0.04||1.05 ± 0.08|
|2011||17||0.20 ± 0.05||0.37 ± 0.08||0.57 ± 0.05||1.03 ± 0.08|
|2010||6||0.32 ± 0.05||0.58 ± 0.08||0.69 ± 0.05||1.24 ± 0.08|
|Uncertainties indicate 95% confidence range.|
The global mean temperature in 2019 was estimated to be 1.28 °C (2.31 °F) above the average temperature of the late 19th century, from 1850-1900, a period often used as a pre-industrial baseline for global temperature targets.
The temperature uncertainties can be visualized using the schematic below where each year’s temperature estimate is represented by a distribution reflecting its uncertainty. In the analysis that Berkeley Earth conducts, the uncertainty on the mean temperature is approximately 0.05 °C (0.08 °F) for recent years. The global mean temperature in 2019 fell between those observed 2016 & 2017 with a modest uncertainty in the true ranking due to overlapping uncertainties.
The last five years stand out as a period of significant warmth well above all previous years since 1850. This reflects the long-term trend towards global warming. Though 2019 is slightly cooler than 2016, its temperature remains consistent with the long-term warming trend.
In addition to long-term warming, individual years are also affected by interannual variations in weather. Both 2015 and 2016 were warmed by an extreme El Niño event that peaked in Nov/Dec of 2015 and was reported by NOAA as essentially tied for the strongest El Niño ever observed. That exceptional El Niño boosted global mean temperatures in 2015 and 2016. By contrast, 2019 began with a weak El Niño event and finished with neutral conditions. This largely neutral weather pattern would not be expected to have had a large impact on temperature in 2019. Internal weather variability, such as El Niño and La Niña, generate year-to-year variations in temperature that occur in addition to the long-term warming trend.
Temperature Distribution in 2019
The following map shows the degree to which local temperatures in 2019 have increased relative to the average temperature in 1951-1980.
As can be expected from global warming caused by greenhouse gases, the temperature increase over the globe is broadly distributed, affecting nearly all land and ocean areas. In 2019, 88% of the Earth’s surface was significantly warmer than the average temperature during 1951-1980, 10% was of a similar temperature, and only 1.5% was significantly colder.
We estimate that 9.9% of the Earth’s surface set a new local record for the warmest annual average. In 2019, no places on Earth experienced a record cold annual average.
The following map qualitatively categorizes local temperatures in 2019 based on how different they were from historical averages after accounting for the typical climate variability at each location. In a stable climate only 2.5% of the Earth would be expected to have temperatures “Very High” or higher in any given year. In 2019, 52% of the Earth have annual averages that would rate as “Very High” compared to the historical climate, including large portions of the tropics. Locations with new records for annual average temperature are also indicated.
Land areas generally show more than twice as much warming as the ocean. When compared to 1951-1980 averages, the land average in 2019 has increased 1.32 ± 0.04 °C (2.38 ± 0.08 °F) and the ocean surface temperature, excluding sea ice regions, has increased 0.59 ± 0.06 °C (1.06 ± 0.11 °F). As with the global average, 2019 was the 2nd warmest year on land. For the ocean surface, we find that 2019 nominally ranks as the 3rd warmest year. However, the differences between the 1st, 2nd, and 3rd warmest years in the ocean are small compared to the measurement uncertainty, meaning they are all essentially indistinguishable. We take note of the fact that other groups have announced that 2019 set a new record for total ocean heat content, including both surface and subsurface waters. The following figure shows land and ocean temperature changes relative to the average from 1850 to 1900. The tendency for land averages to increase more quickly than ocean averages is clearly visible.
As in other recent years, 2019 also demonstrated very strong warming over the Arctic that significantly exceeds the Earth’s mean rate of warming. This is consistent with the process known as Arctic amplification. By melting sea ice, warming in the Arctic regions causes more sunlight to be absorbed by the ocean, which allows for yet more warming. 2019 was the 2nd warmest year in the Arctic.
Both the tendency for land to warm faster than ocean and the higher rate of warming over the Arctic are expected based on our understanding of how increases in greenhouse gas concentrations will impact the Earth’s climate. As has been reported by the Global Carbon Project and other observers, 2018 saw new records for both the level of carbon dioxide in the atmosphere and the annual amount of carbon dioxide emitted by human activities.
National Average Temperature
Though the focus of our work is on global and regional climate analysis, it is also possible to use our data to estimate national temperature trends.
In our estimation, 2019 was the hottest year since instrumental records began in the following 36 countries: Angola, Australia, Belarus, Belize, Botswana, Bulgaria, Cambodia, Comoros, Djibouti, Gabon, Guatemala, Hungary, Jamaica, Kenya, Laos, Latvia, Lithuania, Madagascar, Mauritius, Moldova, Myanmar, Namibia, Poland, Republic of the Congo, Romania, Serbia, Slovakia, Somalia, South Africa, Taiwan, Thailand, Tuvalu, Ukraine, Vietnam, Yemen, and Zimbabwe. In addition, it was also the warmest year thus far observed in Antarctica.
The following chart provides a summary of the warming that countries experienced in 2019 relative 1951 to 1980 averages.
These estimates for the changes in national annual average temperatures are derived from our global temperature fields. Due to uncertainties in the analysis and the limits of our spatial resolution some national average estimates may differ slightly from the values reported by national weather agencies.
Monthly Temperature Pattern
Every month in 2019 was at least 1.1 °C (2.1 °F) warmer than the 1850 to 1900 average. Three months (June, July, and September) set a new monthly record for the globe, and no month ranked lower than 4th.
Though it is interesting to understand the characteristics of individual years, global warming is ultimately about the long-term evolution of Earth’s climate. The following chart shows a ten- year moving average of the Earth’s surface temperature, plotted relative to the average temperature from 1850-1900.
Since 1980, the overall trend is +0.19 °C/decade (+0.34 °F/decade) and has changed little during this period. By continuing this trend, we can make a rough guess of how the near-future climate may develop if the forces driving global warming continue at their present rate.
As shown in the chart, several recent years have had temperatures more than 1 °C (1.8 °F) above the average temperature from 1850-1900, often used as an estimate of the pre-industrial climate. The Paris Agreement on Climate Change aims to keep global temperature rise to well below 2 °C (3.6 °F) and encourages parties to strive for warming of no more than 1.5 °C (2.7 °F). At the current rate of progression, the increase in Earth’s long-term average temperature will reach 1.5 °C (2.7 °F) above the 1850-1900 average by around 2035 and 2 °C (3.6 °F) will be reached around 2065. The increasing abundance of greenhouse gases in the atmosphere due to human activities is the direct cause of this recent global warming. If the Paris Agreement’s goal of no more than 2 °C (3.6 °F) warming is to be reached, significant progress towards reducing greenhouse gas emissions needs to be made soon.
Prediction for 2019
Based on historical variability and current conditions, it is possible to roughly estimate what global mean temperature should be expected in 2020. Our current estimate is that 2020 is likely to be similar to 2019 but with a potential to be somewhat warmer or cooler. It appears highly likely (~95% chance) that 2020 will be one of the five warmest years. In addition, we estimate a roughly 20% chance that 2020 could set a new record for warmest year.
Comparisons with other Groups
When preparing our year-end reports, Berkeley Earth traditionally compares our global mean temperature analysis to the results of five other groups that also report global mean surface temperature. The following chart compares Berkeley Earth’s analysis of global mean temperature to that of the NASA’s GISTEMP, NOAA’s GlobalTemp, the UK’s HadCRUT, Cowtan & Way, and ECMWF‘s reanalysis.
All of the major surface temperature groups except HadCRU have also ranked 2019 as the 2nd warmest year. HadCRU has 2019 as the 3rd warmest year.
The slight disagreement in the ranking reflects both the uncertainty in these estimations and the differences in how various research programs look at the Earth. For example, the NOAA and HadCRU efforts omit most of the polar regions when estimating mean temperature changes. As a result, some groups are unable to capture the strong Arctic warming observed by Berkeley Earth, ECWMF, and others.
In reconstructing the changes in global mean temperature since 1850, Berkeley Earth has examined 20 million monthly-average temperature observations from 48,000 weather stations. Of these 20,000 stations and 210,000 monthly averages are available for 2019.
The weather station data is combined with sea surface temperature data from the UK Met Office’s Hadley Centre (HadSST). This ocean data is based on 392 million measurements collected by ships and buoys, including 18 million observations obtained in 2019. We reprocess and interpolate the HadSST data to provide a more complete picture of the oceans. After combining the ocean data with our land data, we arrive at a global picture of climate change since 1850.
Uncertainties arise primarily from the incomplete spatial coverage of historical weather observations, from noise in measurement devices, and from biases introduced due to systematic changes in measurement technologies and methods. The total uncertainty is much less than the long-term changes in climate during the last 150 years.
This report is based on such weather observations as had been recorded into global archives as of early January 2020. It is common for additional observations to be added to archives after some delay, an issue that is more likely this year due to the US government shutdown. Consequently, temperature analysis calculations can be subject to revisions as new data becomes available. Such revisions are typically quite small and are considered unlikely to alter the qualitative conclusions presented in this report.
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