Sentinel-2 True Colour Image of the south west of the UK, acquired on the 12th July 2025. Image courtesy of Copernicus Data Space Ecosystem.

As everyone knows the British love to talk about the weather, and in the UK we are currently in our official fourth heatwave of the year. A heatwave is declared when temperatures meet or exceed the heatwave temperature threshold for at least three consecutive days – the threshold varies across the country, with temperatures of 28 degrees C being the threshold for London; and 25 degrees C for Wales, Scotland and the South West; with the rest of the country between these two. Now, before anyone gets in touch, we know for some of you these temperatures would only be considered mildly warm, not a heatwave: but remember we are in the UK!

While we would expect to have one or two heatwaves each year, four is quite unusual – although, admittedly, the previous time this happened was only a few years ago in 2022. Research does indicate that heatwaves are becoming more prevalent in the country as the climate warms. Understanding heatwaves is important as not only do they cause travel disruption, but they increase demand on healthcare services – particularly the elderly and those with health conditions. During the record high temperatures of the 2022 heatwave, its estimated that there were approximately 3 000 more deaths in the over-65s than usual in England and Wales.

The additional heat is not the only problem; the lack of rain is also an issue as this week the UK’s National Drought Group warned that England is now suffering from a ‘nationally significant’ water shortfall that is impacting crop growth, damaging river wildlife and wetlands, and increasing wildfire risk.

As an article published this week noted, satellite data has been increasingly used in recent years to detect and monitor droughts as it allows for more frequent measurements than traditional ground-based systems, and it is particularly useful for remote areas. There are several indices that can monitored via satellite data including:

• Vegetation stress through the Normalized Difference Vegetation Index (NDVI)
• Soil moisture levels from satellites such as SMAP (Soil Moisture Active Passive).
• Land Surface Temperature (LST)
• Rainfall

Combining these indicies can also create further insights such as the Vegetation Health Index, which combines NDVI with LST. Over the years Pixalytics have developed different versions of these indices, including combined indicies such as:

• Combined Drought Indicator based on the research of Sepulcre-Conto et al (2012) that brought together measurements of precipitation, soil moisture, and vegetation stress as part of the Open Geospatial Consortium’s Disaster Pilot 2023, and
• Health Impact Demonstrator in the Open Geospatial Consortium’s Climate & Disaster Resilience Pilot 2024 that produced an indicator to assess heat stress risks, by analysing the combined effects of drought and temperature extremes on vulnerable populations and identifying regions at higher risk of heat and drought impacts to supporting urban planning and emergency preparedness.

It’s not only the indices developed from satellite data, but there are also individual satellites collecting data that can be used to help better understand the water cycle and usage such as, NASA’s Gravity Recovery and Climate Experiment (GRACE) mission measuring changes in Earth’s gravity field to monitor underground water reserves termed aquifers.

Humanity depends on water for survival and it therefore it is vital that we understand how the climate is changing and the impacts this could have on the frequency, intensity and location of droughts. It is, therefore, disappointed to hear rumours coming out the United States that the Trump Administration has reportedly asked NASA to prepare to prematurely end the mission of its Orbiting Carbon Observatory-1 and -2 (OCO-1 and OCO-2), which monitor atmospheric carbon dioxide and crop health. The data from these satellites have helped scientists better understanding how the climate is evolving, including identifying the role coniferous forests in the higher latitudes of the northern hemisphere play in absorbing greenhouse gases, and producing global high-resolution maps of plant and crop growth which have been used to determine crop yields and monitor drought conditions.

Despite their success the satellites are being ended apparently to align with the President’s agenda and budget priorities. There is currently a budget proposal to go through Congress, but if approved it will mean the satellites are no longer funded in the last quarter of this year.

Conclusion

The planet’s climate is evolving, and this has different impacts in different locations. Clearly, in the UK we’re facing a warming climate and increased frequency of heatwaves. Using satellite data can play a critical role in helping everyone one and respond to these changes, but to do that we need the satellites to stay in orbit and be collecting data!