The World Scientists' Warning to Humanity was a document written in 1992 by Henry W. Kendall and signed by about 1,700 leading scientists. 25 years later, in November 2017, 15,364 scientists signed World Scientists' Warning to Humanity: A Second Notice written by William J. Ripple and seven co-authors calling for, among other things, human population planning, and drastically diminishing per capita consumption of fossil fuels, meat, and other resources. The Second Notice has more scientist cosigners and formal supporters than any other journal article ever published.
First publication
In late 1992, the late Henry W. Kendall, a former chair of the Union of Concerned Scientistsboard of directors, wrote the first warning World Scientists' Warning to Humanity, which begins: "Human beings and the natural world are on a collision course." A majority of the Nobel Prize laureates in the sciences signed the document; about 1,700 of the world's leading scientists appended their signature. It was sometimes offered in opposition to the Heidelberg Appeal—also signed by numerous scientists and Nobel laureates earlier in 1992—which begins by criticizing "an irrational ideology which is opposed to scientific and industrial progress, and impedes economic and social development." This document was often cited by those who oppose theories relating to climate change. However, the Heidelberg Appeal offers no specific recommendations and is not an indictment of environmental science: "We fully subscribe to the objectives of a scientific ecology for a universe whose resources must be taken stock of, monitored and preserved. But we herewith demand that this stock-taking, monitoring and preservation be founded on scientific criteria and not on irrational pre-conceptions." In contrast, the UCS-led petition contains specific recommendations: "We must, for example, move away from fossil fuels to more benign, inexhaustible energy sources to cut greenhouse gas emissions and the pollution of our air and water. ... We must stabilize population."
Second Notice
In November 2017, 15,364 scientists signed World Scientists' Warning to Humanity: A Second Notice written by lead author professor of ecology, William J. Ripple of Oregon State University, along with 7 co-authors calling for, among other things, limiting population growth, and drastically diminishing per capita consumption of fossil fuels, meat, and other resources. The Second Notice included 9 time-series graphs of key indicators, each correlated to a specific issue mentioned in the original 1992 warning, to show that most environmental issues are continuing to trend in the wrong direction, most with no discernible change in rate. The article included 13 specific steps humanity could take to transition to sustainability. The Second Notice has more scientist cosigners and formal supporters than any other journal article ever published. The full warning was published in BioScience and it can still be endorsed on the Scientists Warning website.
2019 warning on climate change
In November 2019, a group of more than 11,000 scientists from 153 countries named climate change an "emergency" that would lead to "untold human suffering" if no big shifts in action takes place:
