How is the global average surface temperature today different from what it was in 1900 overall change )?

Climate Change Indicators

The Earth’s average surface temperature has increased by about 1.8°F (1.0°C) since the late 1800s.
Human-caused greenhouse gas emissions are responsible for the observed warming.
A warmer Earth also experiences more extreme weather events, like longer fire seasons, bigger and more frequent floods, and slower and stronger hurricanes.

The world is undoubtedly warming. The Earth’s average surface temperature has increased by about 1.8°F (1.0°C) since the late 1800s.

The 10 warmest years on record (since 1880) have all occurred since 1998, and all but one happened since 2005. See a list of global average annual temperatures here.

Light from the sun passes through the atmosphere and is absorbed by the Earth’s surface, heating it up. That energy is then emitted back to the atmosphere. Greenhouse gases, like carbon dioxide and methane, in the atmosphere act like a blanket, absorbing this energy and preventing it from escaping into space. In the absence of a greenhouse effect, the average temperature at the Earth’s surface would be approximately 0 degrees F, about 60 degrees F colder than Earth’s current average temperature. Thus, the greenhouse effect is very important to the survival of life on Earth. But the growing concentration of greenhouse gases from human activities is making this blanket thicker, and warming the planet, which has impacts on ecosystems and our way of life.

The warming of the Earth is largely the result of emissions of carbon dioxide (CO2) and other greenhouse gases from human activities. These activities include burning fossil fuels, such as coal and oil, and changes in land use, such as agriculture and deforestation.

Carbon dioxide concentrations in the atmosphere have increased since pre-industrial times from 280 parts per million to over 400 parts per million.

It is extremely likely that human influence is the dominant cause of the observed warming since the mid-20th century.

The reason for the accumulation is simple: Human activities are emitting more carbon dioxide than the planet’s natural processes (uptake by plants and the ocean) can remove. It’s like a bathtub where the flow of water out of the faucet is more than the flow through the drain, causing the water level in the bath to rise.

This 5-minute video by the National Academies of Sciences, Engineering, and Medicine shows the many lines of evidence that human activities are causing greenhouse gases to increase.

Among the evidence:

Ice cores from Greenland and Antarctica tell us that carbon dioxide and other greenhouse gas concentrations were relatively stable for thousands of years, but began to rise around 200 years ago, when humans began to engage in large-scale agriculture and industry. Concentrations of these gases are now higher than at any time for which we have ice core records, which stretch back 800,000 years.
Carbon dioxide from fossil fuels has a certain isotopic “signature” (an indication of atomic weight) that differs from other sources of CO2. Scientists measure the different isotopes, which confirms that the increase in carbon dioxide in the atmosphere is predominantly from fossil fuel combustion.
Some greenhouse gases, such as industrial halocarbons, are only made by humans. Their accumulation in the atmosphere can only be explained by human activity.

Other factors capable of changing the climate, like volcanic eruptions and changes in the sun’s intensity, cannot by themselves explain the changes we’ve recently observed in the Earth’s climate. The figure below shows the outcomes of different computer simulations of climate (see caption for details). Only the simulations that included human influences exhibited warming similar to the observed temperatures.

Figure 1a. Earth’s global average surface temperature has risen as shown in this plot of combined land and ocean measurements from 1850 to 2019, derived from three independent analyses of the available data sets. The temperature changes are relative to the global average surface temperature of 1961−1990. Source: NOAA Climate.gov; data from UK Met Office Hadley Centre (maroon), US National Aeronautics and Space Administration Goddard Institute for Space Studies (red), and US National Oceanic and Atmospheric Administration National Centers for Environmental Information (orange). (larger version)

The clearest evidence for surface warming comes from widespread thermometer records that, in some places, extend back to the late 19th century. Today, temperatures are monitored at many thousands of locations, over both the land and ocean surface. Indirect estimates of temperature change from such sources as tree rings and ice cores help to place recent temperature changes in the context of the past. In terms of the average surface temperature of Earth, these indirect estimates show that 1989 to 2019 was very likely the warmest 30-year period in more than 800 years; the most recent decade, 2010-2019, is the warmest decade in the instrumental record so far (since 1850).

Figure 1b. A large amount of observational evidence besides surface temperature records shows that Earth’s climate is changing. For example, additional evidence of a warming trend can be found in the dramatic decrease in the extent of Arctic sea ice at its summer minimum (which occurs in September), the decrease in June snow cover in the Northern Hemisphere, the increases in the global average upper ocean (upper 700 m or 2300 feet) heat content (shown relative to the 1955–2006 average), and the rise in global sea level. Source: NOAA Climate.gov (larger version)

A wide range of other observations provides a more comprehensive picture of warming throughout the climate system. For example, the lower atmosphere and the upper layers of the ocean have also warmed, snow and ice cover are decreasing in the Northern Hemisphere, the Greenland ice sheet is shrinking, and sea level is rising [Figure 1b]. These measurements are made with a variety of land-, ocean-, and space-based monitoring systems, which gives added confidence in the reality of global-scale warming of Earth’s climate.

Page last updated: March 2020

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