The popular diktat "you can't manage what you can't measure" encapsulates the role of satellite data in continuous monitoring and measuring of climate change. In fact, according to the Global Climate Observing System, more than 50% of Essential Climate Variables, which are key indicators of the earth's changing climate, can only be tracked via satellites. For instance, the European Space Agency's (ESA's) Climate Change Initiative generates reliable and long-term data for 21 Essential Climate Variables. This wide array of satellite data helps identify our vulnerability to climate change by monitoring and predicting extreme climatic events, such as floods, wildfires, droughts, heatwaves and melting of glaciers, among others.
Role of Satellites in Assessing Indicators of Climate Change
Satellite imagery is a key tool used to study the changing climatic pattern. As most climate variables can be monitored by space, satellites provide a wealth of valuable information to understand the drivers and impact of climate change. Currently, there are around 162 satellites in orbit that are continuously monitoring various climate variables, including the following:
Wildfires
There has been a sharp rise in the occurrence and intensity of wildfires in recent years. As the fire seasons get more extreme, it is estimated that about 3.5 to 4.5 million square kilometres (km2) of vegetation worldwide is burnt every year due to fires. This is equivalent to the size of the entire European Union. As wildfires are closely associated with climate change, they tend to reinforce each other mutually, thus exacerbating the ongoing crisis. Accordingly, as the crisis worsens, monitoring fires could play a huge role in minimizing risks. Traditional systems that use IoT monitors and cameras lack efficiency as it is time-consuming in addition to being expensive. In contrast, satellites have emerged as an effective monitoring infrastructure, making it possible to observe extensive areas in real-time. Data from satellites also provide valuable insights into wildfire behavior, such as their patterns and preferred course.
This, along with other essential information such as vegetation in the region, weather conditions that instigate fires, etc., can help create maps of potential fire hotspots and even help predict fires. Owing to their high temporal resolution and capability to detect fires in remote areas, the US National Oceanic and Atmospheric Administration (NOAA) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellites have played a significant role in detecting fires globally. Similarly, NASA has two satellite systems that help in tracking wildfires: polar orbiters and geostationary platforms. Polar orbiters include NASA's Terra and Aqua satellites and NASA-NOAA's Suomi NPP satellite which give comprehensive views of fires and smoke globally up to twice a day.
Floods
Climate change is causing floods to become increasingly intense and frequent. With respect to this, a study revealed that the percentage of the global population at risk from flooding has risen by almost a quarter since 2000. Accordingly, credible data is of utmost importance as it can help in mapping and managing floods and potentially even accurately predicting them. Satellite data has gained prominence in this context as it can address the persisting data gap.
Owing to its vantage point, satellites provide information on the global occurrence of floods in near real-time. It also helps in understanding the scale and extent of flooding. For example, researchers used NASA's TOPEX/Poseidon satellite and ESA's ENVISAT satellite to calculate the height and extent of flooding in various regions.
Satellite imageries are also helpful in creating predictive models that could help forecast floods. Here, satellites use weather patterns to calculate the tentative amount of rain each area might receive. Spatial images of the ground also enable the calculation of the water retention capacity of the ground. In addition, NASA's Tropical Rainfall Measuring Mission (TRMM) satellite provides scientists with insights into the soil's moisture content. This is a key factor which helps in estimating the chances of the occurrence of floods. These crucial bits of information cumulatively help in developing flood risk maps. This further helps authorities to predict floods and be better prepared to manage them.
The use of high spatial and temporal resolution of satellite observations aid in furthering our understanding of how floods occur and change course. This wide set of information helps not only in increasing the accuracy of flood models but also in improving the efficiency of adaptation strategies.
Heat Waves
As the planet's temperature increases, heat waves too have become more intense. The two crises are closely associated, with studies showing that climate change has increased the probability of heat waves. As countries around the world struggle through these bouts of acute heat, the importance of extreme heat forecasts to be more precise and reliable increases. Satellites, in this regard, play an important role in improving our understanding of the increasingly warming climate and accurately forecasting temperature in different regions. It also provides insights into the occurrence of heat waves. For example, the Copernicus Sentinel 3's Sea and Land Surface Temperature Radiometer generated maps of Turkey and Cyprus during extreme heatwaves. This was helpful since weather forecasts used predicted air temperatures, whereas this satellite instrument calculated the real amount of energy radiating from the earth and conveyed the actual temperature of the land surface.
Satellites also help in forecasting locations in urban regions that are most affected by heat waves. Recognising the importance of increasing our resilience to heat waves, several new efforts are being taken. For example, through its Climate Change Initiative Land Surface Temperature project, the ESA is developing technologies that can assess temperature using satellite measurements. Through this project, It aims to develop capabilities to detect smaller changes in the climate with greater accuracy.
Droughts
Climate change is causing droughts to become more frequent and severe. As the impact is far-reaching, ranging from affecting water quality, public health, economy and public infrastructure, among others, monitoring and predicting droughts has become vital in managing the crisis.
Satellites also play an important role in predicting droughts. They do this by measuring radiation, which helps in accurately measuring soil moisture levels. This provides beneficial insights into weather conditions. For example, if satellite measurements find that soil is getting increasingly wet, it may indicate that a flood is imminent. Likewise, if it finds the moisture content in soil drying up, it could be an indicator of a potential drought. For instance, the Advanced Scatterometer (ASCAT) on board EUMETSAT's polar-orbiting Metop satellites measure moisture content in soil among other things.
Remote sensing also tracks factors such as weather patterns and wind speed which influence weather conditions such as droughts. In addition, satellites also help in assessing the impact of droughts on vegetation. For example, the satellite-based Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) helps assess the impact of droughts.
Additionally, data provided by meteorological and environment-monitoring satellites are helpful in detecting signs of drought. Information on weather conditions also equips the authorites to better respond to such disasters. For example, NASA satellites provide information regarding water availability to the U.S. Drought Monitor. This data further helps farmers be better prepared for droughts. Similarly, a group of satellites called the Joint Polar Satellite System, helps in monitoring severe weather conditions, including droughts.
Deforestation
Deforestation is one of the most pressing challenges we face today, as the world’s tropical rainforests were estimated in 2019 to disappear at the rate of one football pitch every six seconds. Deforestation exacerbates the climate change crisis as it emits huge amount of greenhouse gases. As the crises worsens, monitoring deforestation has become extremely important. With traditional methods such as forest guards having been found to be expensive and time-consuming, satellite data has revolutionized the monitoring of deforestation with high-resolution data. Satellites in this regard present imageries of earth on a daily basis which help in mapping deforested areas over a period of time and in identifying hotspots.
A new study has also found that satellites are helpful in bringing down deforestation. Earth-orbiting satellites were found useful in reducing deforestation by 18% over two years in 22 African countries. These countries took the help of systems that used up-to-date satellite data to send out alerts regarding decreases in forest cover in the tropics. Similarly, the Brazilian government established a data-collection system called PRODES which uses high-resolution data from Landsat 5 and 7 satellites to monitor and map deforestation.
Rising Sea Level
Rising sea levels are one of the most evident indicators of global warming. Melting of seasonal snow and ice cover can cause positive feedback by lowering the albedo of the earth’s surface, and the latter contributes to sea-level rise. The rise in sea level in turn drives coastal erosion and increases storm surges. As a result, monitoring changes in sea levels has become extremely important.
By using satellites, it is possible to measure the changes in sea level all down to a single millimeter. Since the 90s, satellites have been carrying radar altimeters that can track the changing height of ocean surfaces. Some of these satellite missions include the French-US series of Jason satellite missions, ESA’s Envisat and CryoSat missions, and the Copernicus Sentinel-3 satellites. With the advancement of technology, in 2020, an ocean monitoring satellite, the Sentinel 6 Michael Freilich, was launched. It provides ultra-precise measurements of rising sea levels. Satellite data also helps in understanding the major factors that cause a rise in sea levels. This includes thermal expansion caused due to the rising seawater temperature and the addition of freshwater as ice sheets and glaciers lose mass. This information is obtained through specialized sensors placed on Earth-observing (EO) satellites that determine the temperature of the sea surface and changes in ice and glaciers.
Melting of Glaciers
The melting of glaciers is an important indicator of global warming. As the planet is heating up, many glaciers around the world have been shrinking as a consequence of it. Satellite data helps in monitoring the melting of glaciers and in understanding the extent of the crisis. For example, three-dimensional satellite measurements of all the mountain glaciers in the world have revealed that we are losing 31% more snow and ice yearly than 15 years ago. Similarly, the National Aeronautics and Space Administration(NASA), which systematically uses satellite data to monitor the changes in ice sheet volume, provided insights into the rapid melting of ice sheets in Greenland. Their study estimated that an average of 281 billion tons of ice per year was lost between 1993 to 2016.
Apart from monitoring changes, satellite data also helps in predicting future damages. For example, in 2018, at the annual meeting of the American Geophysical Union in San Francisco, scientists released new time series of images from satellites. This series which illustrated glacial retreat over the years, provided warning of the potential retreat of the Hubbard Glacier. Likewise, it shows patterns that provide scientists with clues about factors that drive glacier changes.
In terms of specific satellites, ASTER, Landsat, Copernicus Sentinel-3, Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) and ICESat-2 provide insights into diminishing ice caps and help in monitoring the melting of glaciers.
GHG emissions
Greenhouse gas (GHG) emissions increase the heat in the atmosphere which leads to global warming. These have far-reaching consequences ranging from disrupting food supplies to causing extreme weather conditions such as an increase in sea level, ocean acidification etc. Its impact continues to rise as GHG emissions have increased significantly since the industrial revolution, with studies estimating that it has increased by 70% between 1970-2004. Emissions continue to rise at an alarming pace as GHG concentrations broke record levels in 2021. As long as emissions continue, global temperature will also continue to rise. Thus, monitoring and mapping GHG emissions are crucial in developing strategies to reduce them. Satellite data in this regard plays a prominent role as it has the ability to pinpoint emissions.
In 2009, Japan launched the Greenhouse Gases Observing Satellite (GOSAT), the world's first satellite to monitor greenhouse gases. Since then, several more sophisticated satellites have been launched for the same purpose. At present, the Copernicus Sentinel-5P, launched in 2018 by the European Space Agency (ESA), is known to be the most advanced pollution monitoring satellite in the world. This satellite tracks and attributes methane emissions globally. More recently, in 2021, ESA announced their new space mission, which will be able to track human-caused GHG emissions from space. Scheduled to get operational by 2026, the constellation is said to have the capability to measure CO2 and methane concentrations at a near time in a highly detailed manner with much higher accuracy.
Assessing the Future of Satellites in Monitoring Climate Change
Information is key in combatting climate change. Towards this end, Satellite data has emerged at the forefront of the climate data landscape. It plays a critical role in climate action by providing vital inputs to governments and industries to adapt, prevent and develop resilience to global warming.
In addition, satellite data can make up for the shortcomings of traditional monitoring tools such as IoT monitors, forest guards, etc., which are expensive and time-consuming. The rapid expansion of technology has also enabled unique and precise satellite solutions to various challenges. For example, a major limitation of optical satellites was the lack of clarity due to obscurement by clouds and darkness in mountainous regions. New radars developed can surpass these limitations. New generation satellites also have enhanced optical and temporal resolutions that have improved climate modelling and have capabilities to obtain real-time details. Likewise, the miniaturisation of sensors and high-speed data transfer has made these tools more efficient and precise.
The expansion of technology and innovation in the field thus holds tremendous promise. New satellite missions such as Eumetsat's second-generation polar-orbiting satellites and third-generation Meteosats are expected to have immense value in the coming years. With several path-breaking space 2.0 systems due to be launched in the coming years, clubbed with innovations in artificial intelligence and IoT, the scope of space-based technologies in transitioning into a more sustainable future is immense.
However, while geospatial data has emerged as a near-perfect solution to monitoring indicators of climate change, acquiring insights from its raw form is impossible. To leverage these vast data sets, it is important to run them through sophisticated models. Organisations with strong analytical skills and computational capacity play an important role in integrating valuable data from various sources and disseminating insights through APIs.
