World Scientists' Warning to Humanity

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.[a] The Second Notice has more scientist cosigners and formal supporters than any other journal article ever published.[1]

First publicationEdit

In late 1992, the late Henry W. Kendall, a former chair of the Union of Concerned Scientists (UCS) board 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.[2]

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.[2]

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."[2]

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."[2]

Second NoticeEdit

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.[a] 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.[1] The full warning was published in BioScience[a] and it can still be endorsed on the Scientists Warning website.

2019 warning on climate changeEdit

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:[3][4][5]

We declare clearly and unequivocally that planet Earth is facing a climate emergency. To secure a sustainable future, we must change how we live. [This] entails major transformations in the ways our global society functions and interacts with natural ecosystems.

The emergency declaration emphasized that economic growth and population growth "are among the most important drivers of increases in CO
emissions from fossil fuel combustion" and that "we need bold and drastic transformations regarding economic and population policies".[3]

See alsoEdit


Excerpts and notesEdit

  1. ^ a b c Ripple 2017, pp. 1026–1028: "On the twenty-fifth anniversary of their call, we look back at their warning and evaluate the human response by exploring available time-series data. Since 1992, with the exception of stabilizing the stratospheric ozone layer, humanity has failed to make sufficient progress in generally solving these foreseen environmental challenges, and alarmingly, most of them are getting far worse (figure 1, file S1). Especially troubling is the current trajectory of potentially catastrophic climate change due to rising GHGs from burning fossil fuels (Hansen et al. 2013), deforestation (Keenan et al. 2015), and agricultural production—particularly from farming ruminants for meat consumption (Ripple et al. 2014). Moreover, we have unleashed a mass extinction event, the sixth in roughly 540 million years, wherein many current life forms could be annihilated or at least committed to extinction by the end of this century. Humanity is now being given a second notice, as illustrated by these alarming trends (figure 1). We are jeopardizing our future by not reining in our intense but geographically and demographically uneven material consumption and by not perceiving continued rapid population growth as a primary driver behind many ecological and even societal threats (Crist et al. 2017). By failing to adequately limit population growth, reassess the role of an economy rooted in growth, reduce greenhouse gases, incentivize renewable energy, protect habitat, restore ecosystems, curb pollution, halt defaunation, and constrain invasive alien species, humanity is not taking the urgent steps needed to safeguard our imperilled biosphere. As most political leaders respond to pressure, scientists, media influencers, and lay citizens must insist that their governments take immediate action as a moral imperative to current and future generations of human and other life. With a groundswell of organized grassroots efforts, dogged opposition can be overcome and political leaders compelled to do the right thing. It is also time to re-examine and change our individual behaviors, including limiting our own reproduction (ideally to replacement level at most) and drastically diminishing our per capita consumption of fossil fuels, meat, and other resources."



  • Carrington, Damian (November 5, 2019), "Climate crisis: 11,000 scientists warn of 'untold suffering'", The Guardian, retrieved November 8, 2019
  • Kendall, Henry W. (18 November 1992), World Scientists Warning To Humanity (PDF),, retrieved 2011-08-26
  • Ripple, William J.; et al. (13 November 2017), "World Scientists' Warning to Humanity: A Second Notice" (PDF), BioScience, 67 (12): 1026–1028, doi:10.1093/biosci/bix125
  • Ripple, William J.; et al. (November 5, 2019), "World Scientists' Warning of a Climate Emergency", BioScience, doi:10.1093/biosci/biz088, hdl:1808/30278, retrieved November 8, 2019
  • Suzuki, David (January 6, 2018), "15,000 Scientists Issue Urgent Warning: Humanity Is Failing to Safeguard the Planet", AlterNet, retrieved January 15, 2018
  • Weston, Phoebe (2019-11-05), "11,000 scientists declare global climate emergency and warn of 'untold human suffering'", The Independent, retrieved 2019-11-07

External linksEdit