The Obama Administration on Tuesday released a report showing climate disruption is already leaving deep imprints on every sector of the environment and that the consequences of these changes will grow steadily worse in coming decades.
The 196-page report crisscrosses the United States and finds that global warming has touched every corner: Heavier downpours, strengthened heat waves, altered river flows and extended growing seasons.
These changes, the report notes, will place increasing stress on water, health, energy and transportation systems and have, in several instances, already crossed tipping points to irreversible change.
"This report is a game-changer," said Administrator Jane Lubchenco of the National Oceanic and Atmospheric Administration. "Much of the foot-dragging in addressing climate change is in the perception that climate change is a ways down the road and only occurring in remote parts of the planet.
"Climate change is happening now. It's happening in our own backyards, and ... it affects you and the things you care about."
The report, Global Climate Change Impacts in the United States, is issued every decade by the federal government's Climate Change Science Program. It is an attempt to consolidate and transcribe into accessible language the latest climate science across a broad spectrum of disciplines and regions.
The latest version, more than a year in the making, reiterates findings that global warming is unequivocal and primarily caused by humans from the burning of fossil fuels, the clearing of forests, and the disruption of agricultural activities.
Its focus on such a broad swathe of everyday life and its release at a White House press conference by President Obama's top science and climate advisors was seen by many on Tuesday as an attempt to rally the U.S. public to action.
"It's not a document for scientists. It's not even a document for policymakers," said Katharine Hayhoe, a geosciences professor at Texas Tech University and one of 28 report co-authors.
"It's a document for every individual citizen who wants to know why they should care about climate change."
The report notes that reducing carbon dioxide emissions could lessen warming this century and beyond. But it makes equally clear that climate-related changes are already being observed globally and that new problems and challenges will develop no matter how radically emissions are reduced in the future.
For instance, since 1900 global average temperatures have risen 1.5ºF and are expected to rise another 2ºF given emissions already in the atmosphere but not yet reflected in slow-moving climate systems.
Yet temperatures are rising faster over land than over the ocean and more during the winter than any other season. The result, according to scientists, is that winter temperatures across the Great Plains and Midwest are now some 7º warmer than historical norms.
And that means a reduction in Great Lakes ice cover, which leads to more evaporation, lower water levels, and consequent impacts on shipping, infrastructure, beaches and ecosystems.
Meanwhile the Caribbean and Southeast will see increases in wind, rain and storm surges. California and the Southwest will see drier summers. All will see impacts to human health, water supply, agriculture and other aspects of society, the report's authors concluded.
In Chicago, for instance, annual heat-related deaths per six million people could rise from less than 200 that the city saw in the mid-1970s to almost 700 one generation from now.
In the Northwest, the spring snow pack has already declined 25 percent over the past 40 to 70 years. It will likely shrink another 40 percent by the 2040s, the report said, seriously stressing water supplies, agricultural production and hydropower.
"It's so comprehensive," said Nancy Grimm, a co-author and professor of life sciences at Arizona State University. "This is a right-angle turn from where we've been over the past eight years or so."
Green groups and government watchers praised the report and the Obama Administration's elevation of it on Tuesday. A coalition of 16 science and environmental groups, including the Union of Concerned Scientists, issued a joint statement praising the assessment, while others said it provided much-needed context for sticky debates on Capitol Hill and in statehouses across the land.
"I have not seen the administration talking much about climate change impacts. I see them messaging the climate change legislation in terms of green jobs and green energy and the need to reduce emissions. But why? Why is it so urgent?" asked Rick Piltz, director of Climate Science Watch, a nonpartisan, nonprofit policy watchdog. "This makes the case."
It is, in passages, a downright gloomy case, and several authors on Tuesday said the next report in 10 years hence will likely see a shift in emphasis from mitigation - or avoiding the problem - to adaptation, or learning to live with warming. At least some degree of adaptation will be essential in the future, they agreed, yet how to respond and how much it will cost remains very much unknown.
"It's clear to us already that no matter what we do today, we are going to see some degree of change in the future," Hayhoe said. "We need to understand how we can help our economy, our society, our natural environment .... adjust to coming change."
Still, on Tuesday, there was a sense of optimism. "We can do something about this," said Donald Wuebbles, a co-author and professor of atmospheric science at the University of Illinois. "What we've shown in this assessment is that we need to act soon. Sooner rather than later.
"That's an important part of the finding. We want to avoid the worst of the (impacts) we looked at in these different projections."
Douglas Fischer is editor of The Daily Climate. This article originally appeared at The Daily Climate, the climate change news source published by Environmental Health Sciences, a nonprofit media company.