Take a map of the globe and put a finger on any piece of land, and chances are that it is already being affected by climate change.
Heat waves, flooding and lowered crop yields in recent years are examples of a climate that has already changed with worsening effects to be felt in years to come, said a U.N. panel in a new report.
In the summary of the second report from the fifth assessment of the Intergovernmental Panel on Climate Change (IPCC), released today, scientists warned that the effects of climate change are being felt and that failure to take action to curb additional climate change would result in dire consequences for humans and for natural systems.
"We are not in an era where climate change is some kind of future hypothetical," said Chris Field, a Stanford University scientist who served as the co-chairman of this report, during a press conference about the summary.
This latest report, known as the Working Group II report, focuses on the impacts of climate change and human society's ability to adapt.
The IPCC issued a report on the science of climate change, known as the Working Group I report, late last year, and in two weeks, the body will release a third report outlining options to curb emissions of greenhouse gases.
According to the summary of this latest report, a 49-page document meant to convey the key points of the much larger full report, the world is already committed to a certain level of impacts from global warming.
Impacts seen in typhoons, flooding, food
Some of those impacts are being seen, as evidenced in dramatic, life-destroying events like Typhoon Haiyan, in which flooding was worsened because of sea-level rise in the Philippines.
People in developing nations like the Philippines and in other low-lying island countries and the poor will be more vulnerable to the effects of a changing climate, the report says.
But global warming impacts are not limited to certain areas or populations -- they are spread across the world.
"Nobody on this planet is going to be untouched by the impacts of climate change," said Rajendra Pachauri, chairman of the IPCC, during the press conference.
Some of the major impacts will be felt in areas like water, agriculture and human health. As greenhouse gas concentrations increase, the number of people experiencing both water shortages and major flooding also increases, the report summary says.
In dry subtropical regions, surface water and groundwater resources are expected to decrease, while in high-latitude regions, water resources should increase.
Those areas that experience water shortages are likely to see the price of water go up, said Graham Cogley, a professor at Trent University and a lead author of the report's chapter on freshwater resources.
"In short, we can expect to pay more for water, or people who can't pay will go short. And that is a major problem that global society will face over the course of the 21st century," said Cogley.
Cogley also pointed out the clear difference in water availability and flooding impacts between a world with reduced emissions and one without.
"A high-carbon future will expose more people to the risk of floods," he said.
Human health is also affected by climate change, particularly through the effects of intense heat waves and wildfires, undernutrition from diminished food production and increased risks in food-borne and waterborne diseases, the report states.
And while increased warmth may provide some health benefits in some very cold parts of the world, overall the negative effects outweigh the positive, the report states.
Agriculture is another key area where climate change effects are already being seen and will get worse as the world continues to warm. While positive impacts to crop yields may be experienced in higher latitudes, the overall effects of climate change on crops have been largely negative, the report concludes.
Already, negative impacts on yield have been seen in wheat and corn yields. "Climate change has been an anchor holding back increasing yield," said Stanford's Field.
While until 2050, some crops are expected to see yield increases while others experience decreases, after 2050, the risk of agricultural yield losses increases substantially.
"Global temperature increases of ~4°C or more above late-20th-century levels, combined with increasing food demand, would pose large risks to food security globally and regionally," the report summary states, giving high confidence for that assessment.
Humans can adapt, but there are limits
The report authors were also very confident that coastal areas will increasingly see negative impacts as the globe warms. These include "submergence, coastal flooding and coastal erosion," they wrote.
There is potential for such areas to adapt, said Rebecca Shaw, an associate vice president for ecosystems with the Environmental Defense Fund and a lead author on the adaptation chapter of the report. Shaw gave an example of communities in the Mississippi River Delta investing in a natural system, coastal wetlands, as a way to protect themselves from sea-level rise.
That sort of adaptation using natural ecosystems could be very valuable in the developing world, where expensive, heavily engineered solutions to adapt to climate change are impractical, she pointed out.
But ecosystems themselves also face risks due to climate change. A "large fraction" of species are at risk of extinction due to the combination of climate change and other stressors, including habitat destruction or overexploitation, the report states.
The report also expresses concern about "tipping points," or situations in which, once the Earth's climate is heated enough, "abrupt and irreversible" changes take place. Although scientists are unsure exactly when such tipping points would be crossed, the risk of reaching them increases the more the climate warms.
"That's a risk we have to keep in mind when devising strategies for the future," said Pachauri.
In terms of adaptation to climate change, while it is occurring already, much of the adaptation is in its early phases, said Patricia Romero Lankao, a sociologist with the National Center for Atmospheric Research and a coordinating lead author on the North American section of the report.
However, particularly at the local level, adaptation is taking place with cities and municipalities leading the way, said Romero Lankao and others. The report offers hope in human ingenuity and ability to adapt to things like water stresses or increased flood risks. But there are limits.
A key idea in the report, Romero Lankao noted, is that while humans are capable of adapting to aspects of climate change and overcoming barriers, "we have a closing window of opportunity" to take action.
"We are faced with limits, meaning obstacles that we cannot overcome. There are physical limits to our ability to adapt. And that is why one of our key messages is that we need to adapt and to mitigate today," said Romero Lankao.
Alden Meyer, director of policy and strategy for the Union of Concerned Scientists, pointed out that while many adaptation efforts are geared for the low end of climate change, society should perhaps be adapting for more intense warming scenarios.
"We are on a track to maybe 3.5 to 4 degrees Celsius, maybe more [warming], and on the other hand, we are gauging a lot of our adaptation activities to a 2-degree world. And we really ought to be doing exactly the opposite," Meyer said.
Meyer also noted a shift in this report to a focus on adapting to climate change while also taking actions to decrease emissions, known as mitigation. "I think there has been a shift in the understanding that it's not 'either or,' it's 'both and,'" said Meyer.
Meyer and others also pointed out that investments in adapting to climate change as well as limiting emissions of greenhouse gas can be economic boons, not simply costs. "The investments in both mitigation and adaptation shouldn't be seen as dead-weight losses to the economy. They can be productive investments with co-benefits [like pollution reduction]," Meyer said.
Report can't quantify climate change costs
A possible weakness in the report is its inability to confidently assign costs to climate change.
The summary document says that global economic impacts from climate change are difficult to estimate, varying widely depending on assumption. "Estimates of the incremental economic impact of emitting carbon dioxide lie between a few dollars and several hundreds of dollars per [metric ton] of carbon," it says.
The IPCC's Pachauri argued that standard accounting procedures were inadequate for assessing the cost of climate change.
Field also pointed out that assessing the cost of unchecked warming is "beyond the capability of linear traditional economic approaches."
Anything that does make the costs of climate change more transparent will help the public and policymakers make better decisions on how to address it, said Meyer.
As the report summary was released, representatives from the Obama administration released statements in support of its findings. "Read this report and you can't deny the reality: Unless we act dramatically and quickly, science tells us our climate and our way of life are literally in jeopardy. Denial of the science is malpractice," Secretary of State John Kerry said in a statement.
John Holdren, director of the White House Office of Science and Technology Policy, released a statement saying the new IPCC report "underscores the need for immediate action in order to avoid the most severe impacts of climate change."
Despite controversy, report represents scientific consensus
In creating the report, which rounds up the current science to date and comes to conclusions based on that science, the report authors were able to consider significantly more published literature than for the prior report released in 2007, they said.
The report, 20 chapters long, covers a variety of impacts and also has detailed regional chapters. The summary for policymakers was hashed out in Japan over the course of the last week. The summary is meant to synthesize the main points of the gargantuan report.
During the summarization process, the report authors must agree with the policymakers on precise language, a process that leads to late nights wrangling over sentences and adjectives. There has been some controversy during the process.
A report co-author, Richard Tol, a professor of economics at Sussex University in England, said he dropped out of the summary process last year over concern that the draft of the summary was "too alarmist," he told Reuters.
In response to a question about Tol and whether the report was overly alarmist, Field, the report's co-chairman, said the report is about representing the totality of scientific evidence. "The IPCC report is not about confirming or unconfirming the perspectives of any individual," he said.
"The way I think about it is that when you get an IPCC report, you see the position of the scientific community. Our job is to represent the full diversity of scientific evidence and scientific views," he explained.
Correction: An earlier version of this story misspelled the name of Stanford University scientist Chris Field.
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