Data and code for: A century of reforestation reduced anthropogenic warming in the eastern United States

Restoring and preserving the world’s forests are promising natural pathways to mitigate some aspects of climate change. In addition to regulating atmospheric carbon dioxide concentrations, forests modify surface and near-surface air temperatures through biophysical processes. In the eastern United States (EUS), widespread reforestation during the 20th century coincided with an anomalous lack of warming, raising questions about reforestation’s contribution to local cooling and climate mitigation. Using new cross-scale approaches and multiple independent sources of data, we uncovered links between reforestation and the response of both surface and air temperature in the EUS. Ground- and satellite-based observations showed that EUS forests cool the land surface by 1–2 °C annually compared to nearby grasslands and croplands, with the strongest cooling effect during midday in the growing season, when cooling is 2 to 5 °C. Young forests (20–40 years) have the strongest cooling effect on surface temperature. Surface cooling extends to the near-surface air, with forests reducing midday air temperature by up to 1 °C compared to nearby non-forests. Analyses of historical land cover and air temperature trends showed that the cooling benefits of reforestation extend across the landscape. Locations surrounded by reforestation were up to 1 °C cooler than neighboring locations that did not undergo land cover change, and areas dominated by regrowing forests were associated with cooling temperature trends in much of the EUS. Our work indicates reforestation contributed to the historically slow pace of warming in the EUS, underscoring reforestation’s potential as a local climate adaptation strategy in temperate regions.

Methods
The data utilized in this study is openly available and can be accessed via the links provided below. The data has been processed in accordance with the methodology outlined in the methods section of the paper.

Data
Purpose in Paper
Specific Figure in Paper
URL

Delaware Air Temperature & Precipitation Dataset
Gridded 0.5 ° time series of monthly Ta
Fig 1c,Fig 5d
https://psl.noaa.gov/data/gridded/data.UDel_AirT_Precip.html

North American Carbon Program Forest Age Maps
Gridded 1 km forest age estimates
Fig 1a, Fig 5c
https://daac.ornl.gov/NACP/guides/NA_Tree_Age.html

FOREcasting SCEnarios of Land-use Change  (FORE-SCE) Backcasting Grids
Historical Land Use Change - 250 m resolution
Fig 1b, Fig 5b, Fig 5d
https://www.sciencebase.gov/catalog/item/59d3c73de4b05fe04cc3d1d1

MODIS Land Surface Temperature Product (MYD11A1v6.1)
Remotely Sensed Surface Temperature
Fig 3a, 3b
https://lpdaac.usgs.gov/products/myd11a1v061/

Ameriflux Tower Data
Tower Data for Paired and Flux Tower Syntheses
Fig 3c, 3d, 4 a-d.
https://ameriflux.lbl.gov/

NEON Tower Data
Tower Data for Flux Tower Synthesis
Fig 4 a-d
https://data.neonscience.org/data-products/DP4.00200.001

National Land Cover Database
30 m Land cover for transect analyses
Fig 4e
https://www.mrlc.gov/data?f%5B0%5D=category%3Aland%20cover&f%5B1%5D=region%3Aconus

Landsat Provisional Surface Temperature
Remotely Sensed Surface Temperature for Transect analyses
Fig 4e
https://www.usgs.gov/centers/eros/science/usgs-eros-archive-landsat-archives-landsat-level-2-provisional-surface

United States Historical Climate Network  (USHCN) Meteorological Station
Historical Air Temperature Data
Fig 5a, 5b
https://www.ncei.noaa.gov/pub/data/ushcn/v2.5/

Daymet
Gridded Mesoscale Air Temperature

Fig 3a, Fig 3b, Fig 4a-d, Fig 4e