Persistent global greening over the last four decades using novel long-term vegetation index data with enhanced temporal consistency


 Identifying long-term global plant growth trends is essential for understanding vegetation responses and the drivers of climate change.

Existing studies have used AVHRR satellite products with long-term global monitoring since the 1980s, but distortion of remaining data has been continuously pointed out due to differences in performance between sensors and the effects of deviation from orbit.

"However, to date, no studies have re-analyzed long-term global plant growth trends by correcting the distortions present in satellite outputs."

 Professor Ryu Young-ryul of Seoul National University led international researchers from UC Berkeley, Columbia University, Reading University, Imperial College London, and Leipzi University to identify the continuously increasing trend of plant growth over the past 40 years by correcting distortions remaining in satellite outputs for a long time. The vegetation index output developed in this study can help understand global plant growth trends and terrestrial ecosystem carbon cycles over a long period of time. This study was published in the Remote Sensing of Environment with the support of the Research Foundation's mid-sized task and Schmidt Futures.

□ Formation of Global Joint Researchers

 An international joint research team including UC Berkeley, Columbia University, Reading University, Imperial College London, and Leipzi University was formed to process/analyze/analyze satellite data for 40 years

□ Improve time series consistency by correcting distortion remaining in existing outputs

 In this study, additional correction was performed by classifying the causes of distortion remaining in the existing output into three categories, and time series consistency was evaluated.

 "The improved time series consistency was verified by performing sensor cross-correction, orbital effect correction, and heterogeneous sensor fusion at 26 global satellite correction sites registered with the USGS."

□ Identifying Global Plant Growth Trends Continuously Increasing Over the Last 40 Years

 In this study, the effects of each cause of output distortion were quantified by comparing and evaluating global plant growth trends at each correction stage over the past 40 years.
For data with all corrections performed and time-series consistency verified, plant growth has continued to increase over the past 40 years, and for raw data with distortion remaining, strong growth trends in the 1980s and 1990s and weakened trends since the 2000s.
 For the output (Red:SNU LTDR) corrected in this study, there was a trend of continuously increasing plant growth. This means that for the output (Blue: LTDR; Black: GIMMS3g) where distortion remains, the global plant growth trend in the 1980s-1990s may be overestimated, and the global plant growth trend in the 2000-2010s may be underestimated.

"In particular, the results from before and after the 2000-2010 corrections confirmed that the trends of plant growth in Northern Hemisphere forests and tropical forests near the equator both of which play significant roles as global carbon sinks may be underestimated."