Expert Report

Each report is produced by a committee of experts selected by the Academy to address a particular statement of task and is subject to a rigorous, independent peer review; while the reports represent views of the committee, they also are endorsed by the Academy. Learn more on our expert consensus reports.

The report examines the status of the science underlying weather modification in the United States. It calls for a coordinated national research program to answer fundamental questions about basic atmospheric processes and to address other issues that are impeding progress in weather modification.

Key Messages

  • Additional advances in observational, computational, and statistical technologies have been made over the past two to three decades that could be applied to weather modification. These include, respectively, the capabilities to (1) detect and quantify relevant variables on temporal and spatial scales not previously possible; (2) acquire, store, and process vast quantities of data; and (3) account for sources of uncertainty and incorporate complex spatial and temporal relationships.
  • Despite this lack of scientific proof, operational weather modification programs to increase rain and snowfall and to suppress hail formation continue worldwide based on cost versus probabilistic benefit analyses.
  • There have been substantial improvements in the ice-nucleating capabilities of new seeding materials.
  • There still is no convincing scientific proof of the efficacy of intentional weather modification efforts. In some instances there are strong indications of induced changes, but this evidence has not been subjected to tests of significance and reproducibility.