An image of Earth captured on Jan. 4, 2015, from the VIIRS instrument aboard NASA's Earth-observing satellite, Suomi NPP.

(NASA)

At a Glance

Global climate change tops the list of the scientists' concerns.The scientistssuggest 13 strategies to help decrease humankind's negative impact on theplanet.

More than 15,000 scientists from around the world have joined together to issuea secondwarning to humanity on the state of the planet, marking the 25th anniversary of a preliminary warning issued in the '90s that called on humankind to "curtail environmental destruction."

The Alliance of World Scientists, an international group of and non-governmental organizations or corporationreleased ""on Monday inthe journal Bioscience.

The letter,spearheaded by Oregon State University ecologist William Ripple,is a followup to theby the Union of Concerned Scientists and at least 1,700 other independent scientists, warning that "a great change in our stewardship of the Earth and the life on it is requiredif vast human misery is to be avoided."

“If not checked, many of our current practices put at serious risk the future that we wish for human society and the plant and animal kingdoms, and may so alter the living world that it will be unable to sustain life in the manner that we know,"scientists, including Union of Concerned Scientistsco-founder,wrote in 1992.

Concerns voiced in the' 90s included a decline in freshwater availability, unsustainable marine fisheries, ocean dead zones, climate change, population growth, declining biodiversity and the destruction of the protective ozone layer.

The scientists' second warning is no less dire and is, in fact, rather condemning.

“Humanity has failed to make sufficient progress in generally solving these foreseen environmental challenges, and alarmingly, most of them are getting far worse,” the scientists note.

The greatest threat to the planet today, according to the alliance, is global climate change.

"Especially troubling is the current trajectory of potentially catastrophic climate change due to rising GHGs from burning fossil fuels, deforestationand agricultural production— particularly from farming ruminants for meat consumption," they write.

The only bright spot noted by the scientists since the release of the first warning is the decrease in the hole in the ozone layer that hovers over Antarctica, which is its. The hole has been slowly recovering thanks to a 1987 international ban on harmful chlorofluorocarbons, chemicals that were onceused in refrigerants and aerosols.

“The rapid global decline in ozone-depleting substances shows that we can make positive change when we act decisively,” the letter points out.

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The scientistssuggest 13 strategies to help decrease humankind's negative impact on theplanet, including the establishment of economic incentives to change patterns of consumption, a reduction of food waste and the development of green technologies.

The alliance notes that unless changes are made, "it will be too late to shift course away from our failing trajectory.”

Still, the scientists remain hopeful that those very changes can be made through commitment and unity.

"It is important to continue this work to document challenges, as well as improved situations, and to develop clear, trackable, and practical solutions while communicating trends and needs to world leaders," the scientists conclude. "Working together while respecting the diversity of people and opinions and the need for social justice around the world, we can make great progress for the sake of humanity."