The National Assessment was mandated by the United States Congress under the Global Change Research Act of 1990.
The National Assessment received criticism from many of those who were involved in its early review. "Critics claimed that many of the model-projected impacts of possible future climate changes were overstated and unsubstantiated. The National Assessment Synthesis Team (NAST), with overall authority for the report, countered that much of the criticism it had received did not take into account the time scales upon which the report was based; the report targeted the effects of climate toward the middle of this century to the end of the next. Also, seemingly contradictory outcomes were produced by the two climate models selected for making the climate projections, casting some lingering doubt on the overall value and utility of the results for decision makers at the local, regional, and national levels. Various regional and resource-focused assessments are now available at the USGCRP website A final synthesis report by the NAST, of the same title and consisting of an overview of all of the regional and sectoral studies, was released in December 2000."
The National Assessment was attacked upon publication by the Competitive Enterprise Institute (CEI), an industry-funded think tank with an anti-regulatory free-market philosophy and a longstanding history of opposing efforts to address global warming. CEI filed lawsuits seeking to have the NACC report declared unlawful and to suppress its dissemination. These suits were dismissed "with prejudice," which means they had so little merit that they could not be refiled. In an interview, James R. Mahoney, admitted that the Climate Change Science Program has been constrained in its ability to use information in the National Assessment.
The NACC report has also been attacked by other industry-funded think tanks, including the American Enterprise Institute. Its critics claim that the report is flawed in its methodology and conclusions.
The National Assessment was followed in 2002 by a new program, the Climate Change Science Program. That program, slated to produce 21 reports, yielded its first in May, 2006.
In 2005, a group of scientists took a second look at the National Assessment and declared it a success. Their report was published in the peer-reviewed journal, Environmental Science & Technology.