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Questions and answers

How do scientists measure the temperature of the Earth?

Have you ever wondered how the increases in the Earth’s temperature are measured?

Many aspects of the earth’s temperature can be measured, each with their own relevance and techniques. These include:

  • near-surface air temperature
  • ground surface and sub-surface temperatures
  • temperature of the atmosphere
  • sea-surface and deep ocean temperatures.

We have the most historic climate temperature data for near-surface air temperature. There are long-term records of this, taken from weather observations over many decades. Today, modern temperature observations are taken in automatic weather stations which use platinum resistance thermometers. These are monitored remotely across a network of locations 

The challenge for weather stations is not the temperature measurement itself, but the effect of external influences. Weather-station housings (screens) are designed to protect the station from solar radiation, rain, and other influences that can cause errors in observed temperatures. Sites are carefully chosen to avoid external influences such as trees, buildings and roads, all of which can falsely raise or lower the temperature values, however these influences can’t always be eliminated. It is a continuing challenge to obtain observations of air temperature that are both accurate and properly represent the surrounding area, and to evaluate the associated uncertainty. NPL works with the UK Met Office and others to improve the measurement and analysis of temperature data for climate.

Climate temperature measurements are underpinned by calibrations traceable to national standards of temperature such as those set by NPL. This links measurements to an international temperature scale that is stable, comparable and coherent. For the climate temperature record, it is vital to have continuity of techniques and their traceability, so that values can be compared over time. For interrelating satellite and ground-based temperatures, and for data used in computer models, coherence is important so that the relevant physics can link across the different results without systematic error. For integrated global climate data, internationally consistent measurements are essential. All these goals are supported by traceability of climate temperature measurements to the SI through national laboratories such as NPL.

what is net zero

Learn more about NPL’s work in support of climate change action and our Measurement for our planet programme




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