PACE maps greening tied 70% to CO2

Plants can look greener for a bunch of different reasons. More leaves. Different pigments. Less stress. More photosynthesis. Or just a seasonal flush that doesn’t mean much long term. That’s the gap PACE is starting to close. NASA’s satellite is not the thing that discovered “CO2 caused 70% of global greening” — that result is older — but it is the tool that could finally show what kind of greening we’re actually getting. (nasa.gov) ### What is PACE actually measuring? PACE is a NASA Earth-observing satellite launched on February 8, 2024. Most people know it as an ocean mission, because it was built to study phytoplankton, aerosols, and clouds. But its Ocean Color Instrument also collects hyperspectral data over land — basically dozens of narrow color bands instead of a few broad ones — at roughly 1.2 km resolution every one to two days. (pmc.ncbi.nlm.nih.gov) ### Why does hyperspectral land data matter? Older satellites were good at showing broad greenness. PACE can go further. It can estimate several plant traits and indices tied to chlorophyll, carotenoids, anthocyanins, water content, and light-use efficiency. That matters because two forests can look equally green while one is thriving and the other is stressed and just changing pigments to protect itself. (tandfonline.com) ### So where did the 70% number come from? That headline comes from a 2016 Nature Climate Change study summarized by NASA. Using long satellite records from AVHRR and MODIS plus multiple vegetation models, the team estimated that rising CO2 explained about 70% of the observed greening trend from 1982 to 2015. The total leaf-area increase was huge — about the area(tandfonline.com) (nasa.gov) ### What did that older study actually show? It showed that from a quarter to half of Earth’s vegetated land had significantly greened over roughly 35 years. The key point was attribution, not just detection. Researchers ran model experiments isolating CO2, nitrogen, climate, and land-cover effects, then checked which mix best matched the satellite record. That is why the result was framed as CO2 fertilization, not just “the world got greener.” (nasa.gov) ### What can PACE add that older satellites couldn’t? PACE can help split one blurry signal into several sharper ones. Instead of asking only “are there more leaves?”, scientists can also ask “which pigments changed?”, “is photosynthetic efficiency rising or falling?”, and “is this area greener because growth improved or becaus(nasa.gov)es that had not previously been produced globally from space. (tandfonline.com) ### Does greener mean climate change is helping plants? Not really — or at least not in the simple way that headline implies. Extra CO2 can boost photosynthesis, especially where water-use efficiency improves, but warming, drought, fire, nutrient limits, and heat stress can erase or reverse that benefit. A greener planet is not automatically a healthier or more s(tandfonline.com)s is only part of the climate story. (nature.com) ### Why are scientists excited now? Because PACE extends the old vegetation record while adding measurements that were mostly local or experimental before. A 2026 overview paper describes the mission as providing novel, near-daily land observations that other current satellites cannot, which means better testing for Earth-system models and fewer guesses about what pigment and productivity changes actually mean. (pmc.ncbi.nlm.nih.gov) ### Bottom line? The real story is not “PACE proved CO2 caused 70% of greening.” That part was published a decade ago. The real story is that PACE is starting to show what that greening is made of — leaf by leaf, pigment by pigment — and that is the difference between seeing Earth get greener and understanding whether it is getting healthier. (nasa.gov)h-study-finds/))