海角大神

In early April, more than a thousand scientists around the world decided to protest. They chained themselves to government buildings, blocked intersections, and staged sit-ins. In Spain, they threw fake blood on the facade of the parliament building. In Los Angeles, police arrested a lab-coated crew who had attached themselves to a JPMorgan Chase building to oppose the financing of fossil fuels.聽聽

鈥淭he scientists of the world have been being ignored,鈥� said NASA climate scientist Peter Kalmus, voice trembling, as he stood with the other Los Angeles protesters. 鈥淚t鈥檚 got to stop. We鈥檙e going to lose everything. ... We鈥檙e not lying; we鈥檙e not exaggerating.鈥澛�

The impetus for these demonstrations was a new report from some 200 authors and a United Nations group called the Intergovernmental Panel on Climate Change (IPCC). For Dr. Kalmus and many others involved in climate research, the document screamed both warning and accusation 鈥� proof that governments, businesses, and individuals must immediately change course to avoid increasingly catastrophic impacts of climate change. It also gave road maps for avoiding worst-case scenarios 鈥� if people will follow them.

But what鈥檚 clear to the scientists isn鈥檛 always straightforward to everyone else.

In a study last year, researchers found that most Americans are confused by terms traditionally used to convey climate information, such as 鈥渢ipping point鈥� or 鈥渕itigation.鈥� Add the acronym-heavy international climate world, with its multiple working groups, assessments, and 鈥淐OPs鈥� that have nothing to do with policing, and it鈥檚 easy to understand why the public鈥檚 reaction to these reports can differ from the scientists鈥�.聽聽

鈥淚 don鈥檛 think people necessarily get how the IPCC works,鈥� says Jacquelyn Gill, a paleoecologist and climate communications expert at the University of Maine. 鈥淎cronyms, scientific jargon, all of those things, they become a persistent bumper in scientific communications.鈥�

What is the IPCC and why does it matter?

The World Meteorological Organization and the U.N. Environment Program joined forces in 1988 to create the IPCC, an international body with the goal of reviewing the science, economic impact, and future threats of climate change. Since then, hundreds of scientists have volunteered every IPCC 鈥渁ssessment period,鈥� which lasts about seven years, to go over tens of thousands of published studies and distill their meaning.聽

鈥淚t鈥檚 taking this mass of knowledge, taking all the experts involved, saying ... 鈥楾his is what we know; this is what policymakers need to know,鈥欌�� says David McCollum, senior scientist at the Oak Ridge National Laboratory in Tennessee and an IPCC author.聽

This 鈥渂ig picture鈥� process is both exhaustive and bureaucratic. The IPCC staff carefully picks scientists to represent different regions and disciplines. Expert reviewers and representatives from the world鈥檚 governments look at what the scientists have written, and negotiate line by line in order to come to a consensus about the summary report.

This last step ensures that U.N. member countries have 鈥渂uy-in鈥� to the reports, explains Katherine Leitzell, a communications specialist who worked with the IPCC.

鈥淭he governments can鈥檛 just come back and say no, that鈥檚 nonsense.鈥�

Within the IPCC, three 鈥渨orking groups鈥� of scientists tackle three big aspects of climate change: the physical science, such as how oceans are warming; who and what is vulnerable and how they might adapt; and mitigation, or ways to reduce greenhouse gas emissions.聽聽

This 鈥渢rilogy鈥� of IPCC work goes alongside another U.N. process, the Conference of the Parties, or COP, which focuses on policymaking.

The IPCC reports are supposed to help policymakers, businesses, municipalities, and even individuals make the most informed climate decisions possible.

What do the IPCC reports actually say?

Even though these reports are based on existing research, they still pack a message.聽

As Inger Andersen, executive director of the U.N. Environment Program, put it in a press conference last month, the first two reports in the IPCC鈥檚 current cycle show that climate change is happening and is causing huge disruption to both the natural and human worlds. The third, most recent report shows that 鈥渨e are still not doing enough to cut greenhouse gas emissions.鈥澛�

A quick pause here. 鈥淕reenhouse gas emissions鈥� means the heat-trapping gases 鈥� such as carbon dioxide, methane, and nitrous oxide 鈥� that humans are releasing into the atmosphere alongside natural volumes of these gases. Carbon dioxide makes up the bulk of these, so that鈥檚 why there鈥檚 a lot of talk about 鈥渃arbon footprints鈥� or 鈥渄ecarbonization.鈥� Most of our carbon emissions come from burning fossil fuels. But we also release carbon dioxide in chemical processes, such as the one that makes cement, or by cutting down trees.聽

The past 20 years saw the highest increase in emissions in human history. And greenhouse gas concentrations in the
atmosphere are also at their highest levels in the history of humans on Earth, researchers say. That means that unless there are big, quick changes, it is all but inevitable that the impacts on human society and the natural world will get more severe.

鈥淭he jury has reached the verdict and it is damning,鈥� said U.N. Secretary-General Ant贸nio Guterres at a press conference in April. The new report 鈥渋s a file of shame, cataloging the empty pledges that firmly put us on track towards an unlivable world. We are on a fast track to climate disaster.鈥�

Back up. Climate disaster?

Well, here鈥檚 the thing about the concept of a climate disaster: Scientists know that with more warming come more negative impacts, and also the chance for natural cycles to reach 鈥渢ipping points,鈥� or moments when normal natural processes unravel, potentially causing even more warming. But it鈥檚 not so easy to describe what 鈥渄isaster鈥� means. Many people already are suffering catastrophic impacts of climate change, such as increased wildfires, deeper drought and crop failure, and extra-severe storms.聽

And what, actually, will happen in the future largely depends on one unknown variable: human behavior.聽

鈥淭he biggest uncertainty when it comes to our climate future is what we do,鈥� says Dr. Gill. 鈥淣ot what the Earth is going to do.鈥�

So what can we do?聽

Humans 鈥� whether operating as governments, businesses, or individuals 鈥� can take steps to either limit warming or allow it to continue exponentially. And across society, we already have the tools to lower emissions. The most recent IPCC report explored how this could happen in various sectors, including transportation, agriculture, and energy, and also in different countries, with their unique economies, development statuses, and existing challenges.

鈥淪cientists and governments know how to reduce emissions quickly,鈥� says Dr. McCollum, whose work with the IPCC focused on assessing models of future warming, under differing scenarios of human behavior. Achieving the most ambitious goals would require massive changes, he says, 鈥渂ut there are things we know how to do now.鈥�

This includes everything from speeding up the electrification of transportation systems (think electric cars and a robust charging station network), to making sure new construction meets stringent energy efficiency standards, to revamping financial systems to ensure adequate funding for experimental climate technology.聽聽

A rapid decrease of fossil fuel use is necessary to quickly lower emissions, the report鈥檚 authors found. And the more we do, and quickly, is better.聽

But scientists caution against seeing climate change as a pass-fail situation, where if the world surpasses a certain warming level 鈥� 1.5 degrees Celsius is the one mentioned regularly 鈥� we鈥檝e 鈥渓ost.鈥澛犅�

鈥淓very fraction of a degree is worth fighting for,鈥� says Dr. Gill. 鈥淎nd that will always be true.鈥�