As 2019 comes to an end and a new decade approaches, we look back at all the important Earth science NASA has revealed. This is a time to take stock in all that we have learned and to use those insights to better understand and reliably predict the many ways our planet is changing in the coming decades.
Our planet is an interconnected system, and every new discovery leads to new understandings and new avenues of exploration. Our climate is changing, and NASA spacecraft and science over the past decade have studied it from numerous angles and perspectives. Below are highlights of the science NASA spacecraft have enabled over the past decade, and important topics to study over the decades to come.
In 2012, the Arctic sea ice cover reached the smallest point observed from space yet, and in the years since, scientists have watched it shrink further. Studying the sea ice loss has brought new insights to the feedback loops that climate change has set in motion. The sea ice cover in the Arctic has, in the past, protected that area of the world from warming. Because ice is a much brighter surface than the dark ocean, it reflected more light and heat. With the loss of that ice, the ocean now absorbs that heat and speeds up warming in the Arctic.
This sea ice loss has also been found to affect the average age of the sea ice, with less and less of the seasonal cover lasting multiple years. Now that much of the multiyear ice has been lost, further changes in ice thickness and age will happen more slowly, as the majority of the sea ice now is seasonal, melting with the summer. Continuing to monitor the Arctic sea ice in the coming years, from airborne and spaceborne platforms, will be critical to understanding the effects of climate change in that region.
In May of 2013, the average global CO2 concentration broke the 400 parts per million (ppm) level, and has since continued to rise. In 2017, the annual minimum CO2 concentration also reached the 400 ppm level, further cementing the importance of tracking the carbon dioxide levels in our atmosphere. Satellite missions like the Orbiting Carbon Observatory 2 (OCO-2) have added space-based global measurements of atmospheric CO2 with the precision, resolution, and coverage needed to characterize sources and sinks (fluxes) on regional scales. The Orbiting Carbon Observatory 3 (OCO-3) was launched in 2019 to expand the horizons of OCO-2 , focusing its instrument on large cities.
When OCO-2 and OCO-3 aren’t studying carbon dioxide, they’re still hard at work measuring plant growth! The OCO-2 science team found that their instrument could also be used to track the tiny amount of glow plants give off when they photosynthesize, and have been studying the health and stress of plants in tandem with the project’s other science objectives
For a student-friendly explanation of the greenhouse effect and how that contributes to rising carbon levels in the atmosphere, visit Climate Kids!
NASA has been continuously studying the ozone hole since it was first discovered, and 2019 has shown the smallest hole yet. Typically, it grows to a size of 8 million square miles, but this past year its maximum was 6.3 million miles. While this is good news for the ozone hole, it is not caused entirely by the repair that began with the signing of the Montreal Protocol on Substances that Deplete the Ozone Layer. With no other systems at play, a decrease in chlorofluorocarbons (CFCs) in the atmosphere after they were banned in 1987 would result in the ozone hole reaching its past levels around 2070.
The Antarctic ozone hole forms during the Southern Hemisphere’s late winter as the returning Sun’s rays start ozone-depleting reactions. These reactions involve chemically active forms of chlorine and bromine derived from man-made compounds. The chemistry that leads to their formation involves chemical reactions that occur on the surfaces of cloud particles that form in cold stratospheric layers, leading ultimately to runaway reactions that destroy ozone molecules. In warmer temperatures, fewer polar stratospheric clouds form and they don’t persist as long, limiting the ozone-depletion process.
The smaller hole is in part because of the decrease in CFCs in the atmosphere, but also because of warming temperatures. In warmer temperatures, fewer polar stratospheric clouds form, and they don’t persist as long, limiting the ozone-depletion process.
NASA and the National Oceanic and Atmospheric Administration (NOAA) study the ozone hole in complementary methods. A trio of NASA satellites measure ozone from space, and Aura’s Microwave Limb Sounder instrument estimates levels of chlorine in the atmosphere. NOAA staff, meanwhile, launch weather balloons from the ground that carry ozone-measuring instruments, providing another set of data to pair with the space-based record.
Both agencies will continue to study the ozone hole and how it is affected by climate change in the coming years.
From a 2015 study showing that fire seasons are growing longer, to the satellite record displaying the similar effects from space, it is becoming clear that the longer and fiercer fire seasons are also an effect of climate change. The satellite record of the past 20 years has shown a large-scale trend of increased fire activity in places experiencing warming temperatures and a drying climate. A drier climate leads to an increase in burning fuel as plants die out and dry up. Further, warmer temperatures at night result in fires lasting multiple days, where cooler temperatures may have suppressed the fire and kept it from spreading as drastically.
NASA is continuing to study fires from space, and has also launched airborne and ground-based Earth Expeditions, such as FIREX-AQ to further study the effects of more frequent fires on our planet and on human health.
Looking for a student-friendly explanation of wildfires? Check out this video: https://scijinks.gov/wildfires/
In May 2019, after the wettest 12 months ever recorded in the Mississippi River Basin, the region was bearing the weight of 8 to 12 inches (200 to 300 millimeters) more water than average. New data from NASA's Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission, which launched in May 2018, showed that there was an increase in water storage in the river basin, extending east around the Great Lakes.
GRACE-FO is a follow-on mission from GRACE, which built a 15-year data record of tracking water mass movement, studying floods, droughts, and ice melt. Some of GRACE’s findings include measuring the melting of both the Greenland and Antarctic ice sheets. The Greenland mass loss trend from April 2002-March 2009 (7 years) is -219 Gigatonnes/year (Gt/yr). The Greenland mass loss trend for the next 7 years, from 2009 to 2016, is -319 Gt/yr. Antarctica’s melt is smaller in magnitude, but there is a more distinct acceleration happening there. For the same seven years, between 2002 and 2009, Antarctica’s trend is -73 Gt/yr. Then, between 2009 and 2016, the trend is -165 Gt/yr. If you’d like to explore and see GRACE’s work yourself, you can access and download the data here.
The twin GRACE-FO spacecraft are used to measure the change in the mass of water across the planet, providing scientists, decision makers and resource managers with an accurate measure of how much water is retained - not only on Earth's surface, but also in the soil layer and below ground in aquifers. Monitoring these changes provides a unique perspective of Earth's climate and has far-reaching benefits for humankind, such as understanding both the possibility and the consequences of floods and droughts.
The continuing work from GRACE-FO will be important in the coming decade as climates around the world change, helping scientists monitor the movement of water around the globe.
2020 and Beyond: Upcoming Missions
NASA’s Earth Science program is ever-evolving, and there are many missions being currently built. Of the many in development, two to keep an eye on are the Surface Water and Topography (SWOT) and NASA-ISRO Synthetic Aperture Radar (NISAR) Missions, both of which will be launching in the next few years. Each new mission being developed will provide a new angle on Earth science, and will help provide a better understanding of the complicated and interconnected systems that govern our planet.
Want to see how your home planet is changing? Explore NASA’s “Images of Change” gallery to see different locations on Earth, showing change over time periods ranging from days to decades.