Humans are warming atmosphere and climate change is irreversible unless we act now.

IPCC graph
Public Domain IPCC

The Intergovernmental Panel on Climate Change (IPCC) has released what surely must be one of the most important science documents of all time. The report, known as the fifth assessment report (AR5), is an assessment of current climate research and the IPCC's conclusions could not be more clear: There is 95% certainty that humans are responsible for warming the atmosphere and if we do not slow the rate of greenhouse gas emissions, climate change will become irreversible.

Here are some of the IPCC's findings:

"Warming in the climate system is unequivocal and since 1950 many changes have been observed throughout the climate system that are unprecedented over decades to millennia. Each of the last three decades has been successively warmer at the Earth's surface than any preceding decade since 1850. In the Northern Hemisphere, 1983–2012 was likely the warmest 30-year period of the last 1400 years.


The atmospheric concentrations of carbon dioxide (CO2), methane, and nitrous oxide have increased to levels unprecedented in at least the last 800,000 years. CO2 concentrations have increased by 40% since pre-industrial times, primarily from fossil fuel emissions and secondarily from net land use change emissions. The ocean has absorbed about 30% of the emitted anthropogenic carbon dioxide, causing ocean acidification.

The full report will be made public next week, but you can read the summary here. None of this is particularly new, but it is the increased confidence that is remarkable.

IPCC graphIPCC/Public Domain

Justin Gillis at The New York TImes reports on the "carbon budget" endorsed by the IPCC:

Going well beyond its four previous analyses of the emissions problem, the Intergovernmental Panel on Climate Change endorsed a “carbon budget” for humanity — an upper limit on the amount of the primary greenhouse gas, carbon dioxide, that can be emitted from industrial activities and forest destruction.

To stand the best chance of keeping the planetary warming below an internationally agreed target of 3.6 degrees Fahrenheit above preindustrial levels and thus avoiding the most dangerous effects of climate change, the panel found, only about 1 trillion tons of carbon can be burned and the resulting gas spewed into the atmosphere.

Just over half that amount has already been emitted since the beginning of the Industrial Revolution, and at current rates of energy consumption, the trillionth ton will be released around 2040, according to calculations by Myles R. Allen, a scientist at the University of Oxford and one of the authors of the new report. More than 3 trillion tons of carbon are still left in the ground as fossil fuels.

Andrew Revkin says the report clarifies humanities choices:

For decades to come, climate trajectories — up or down — will be shaped most by natural variability in the system (as with the recent plateau in temperatures). But humanity, by acting in ways that blunt emissions of greenhouse gases, can significantly affect the rate of warming and other related conditions from mid century onward. That’s a time scale that people can reasonably understand. Energy and environmental policies being considered now can matter not just to great grandchildren, but to many global citizens alive today.


Knowing that some non-scientists or less-scientifically literate readers would hear that scientists were only 95% sure global warming is man-made and conclude that this means scientists aren't really sure, the Associated Press' Seth Borenstein did a good post on what 95% certainty means to scientists.

Top scientists from a variety of fields say they are about as certain that global warming is a real, man-made threat as they are that cigarettes kill.

They are as sure about climate change as they are about the age of the universe. They say they are more certain about climate change than they are that vitamins make you healthy or that dioxin in Superfund sites is dangerous.

"But in science, 95 percent certainty is often considered the gold standard for certainty," writes Borenstein.

ipcc graphIPCC /Public Domain

So where do we go from here? Back to the grind. Individuals need to do better to conserve energy, make things last, avoid waste, etc. Businesses need to do the same and invest in new technologies to help those efforts. Industry must find ways to do business with less pollution. And Governments need to pass legislation to incentivize and pressure all of us to do better.

This week, Denise Chow at LiveScience listed 4 things to know about the IPCC's climate report:

4. The IPCC is considered the world's leading climate change advisory body.
As an intergovernmental organization that includes input from thousands of scientists and experts, the IPCC is considered the authority on climate change and global warming. The group's reports, with their focus on peer-reviewed research, undergo a meticulous review process involving thousands of scientists and government representatives.

"It's the most elaborate review and approval process for any scientific report in the world," said Alden Meyer, the director of strategy and policy for the Union of Concerned Scientists, a science advocacy group headquartered in Cambridge, Mass.

As a result, the findings of the IPCC reports, while conservative, are generally used as benchmarks in the field of climate research.

In other words, we'd be wise to listen to these scientists and work on how to avoid the catastrophic results our current warming is causing.

We already knew we needed to avoid the terrifying math of global warming. This report just confirms those concerns and gives a new, higher level of certainty, which hopefully can help inspire action on solutions.

Humans are warming atmosphere and climate change is irreversible unless we act now.
The Intergovernmental Panel on Climate Change (IPCC) has released its fifth assessment report (AR5), which surely must be one of the most important science documents of all time.

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