A record number of Americans report that global warming is taking place, according to a recent Yale Climate Change Communication Survey and the George Mason University Center for Communications on Climate Change Climate change, and nearly three-quarters of them say it's an issue that matters to them personally. Both numbers have risen sharply in recent years – a shift that could not have come soon enough, as the once-distant turning points and worst case climate scenarios that researchers have been predicting for decades are becoming reality.
This week, for example, researchers have warned that the Greenland ice sheet has reached a turning point. An international team of scientists found that ice losses in Greenland in early 2013 were four times higher than in 2003.
It's not the fact that ice loss accelerates, which was surprising, but where it came from. According to Michael Bevis, a professor at Ohio State University and lead author of the new study, there are two sources of ice loss in Greenland: glacial rocks fall directly into the ocean and run ashore from the melting ice. Climate scientists have known for years that the glaciers of the Arctic nation are drilling faster into the sea as the ocean warms around the island, but their ice cover has been relatively isolated from the increased air temperatures, Bevis says.
In this new study, Bevis and his colleagues were surprised that the largest loss of ice occurred in the southwestern corner of Greenland. a region with very few glaciers. In other words, the biggest loss of ice was in the form of meltwater draining from land-covered ice sheets into the sea.
"We saw a massive acceleration of ice loss through melting: Greenland lost 100 billion tons in 2003, and by the beginning of 2013 it has lost almost 400 billion tons per year," says Bevis. "Then, in the summer of 2013, it stopped, it was amazing."
What Bevis and his colleagues found was that the smelting was controlled by something known as the North Atlantic Oscillation – an irregular fluctuation in atmospheric pressure across the Atlantic, affecting the weather on several continents. The NAO has two phases: a negative phase that brings warm air to Greenland, and a positive phase that brings cold temperatures. The NAO has existed for thousands of years, with little impact on the melting ice in Greenland. What has changed is our atmosphere, says Bevis.
"Global warming brought summer temperatures just below the critical temperature at which massive melting would occur, and the NAO has exceeded this critical threshold," he says. When the NAO returned to the positive phase and colder air returned, the main meltdown stopped. That may sound like good news – a positive NAO can buffer Greenland's ice cap from global warming – but that's certainly not the case, says Bevis. This means that the ice sheet is now sensitive to small variations in summer temperatures, and as global temperatures continue to increase as predicted, Greenland's summer will soon be warm enough to cause massive melting regardless of the NAO's phase.
The researchers were already concerned about Greenland's contributions to sea-level rise, as only icebergs were being pulled off that would slowly melt in the ocean. But meltwater is also a source of sea-level rise, but also disturbing for other reasons. The longer-term concern, says Bevis, is, in about 50 or 100 years, "if you put enough fresh water into the oceans near Greenland, you can disrupt the global circulation system of the oceans."
900-pound gorilla of the climate system, "says Bevis." Basically, there is the climate system to dissipate the heat, so much of this heat transfer occurs through the global ocean circulation systems. "Hot water streams like the Gulf Stream carry warm water From the equator to the poles When the warm water arrives in Greenland, it sinks "If there is a whole lot of fresh water, it does not want to sink, and the conveyor belt slows down," says Bevis "It's hard to say what that But here's the thing with these long-term climate concerns: they tend to arrive much sooner than expected. [19659008Atthebeginningofthismonthresearchersreportedinthejournal Science that the oceans were around 40 percent faster than the United Nations climate panel predicted a few years ago last year, a climate researcher said Guardian that the Antarctic ice sheet is now melting at a "surprising" and accelerating speed. Bevis agreed that quite a few newspapers have been published in recent years saying that the effects of global warming have been underestimated and that they have expired faster than expected.
While melting ice sheets and sea-level rise are attracting much attention, Michael Mann, a climate scientist at Penn State University, points out that climate change also has a dramatic impact on extreme summer weather events. In a October Science Advances article Mann and his colleagues identified a key mechanism by which climate change affects extreme weather events that could not be captured by current climate models: a jet stream that calls itself poorly. The team found that climate change kept the once-snaking jetstream in place, capturing high- or low-pressure systems in the atmosphere that led to extreme heat waves, drought, forest fires and extreme fires in the summer of 2018 the United States and abroad.
"In other words," writes Mann in an e-mail, "climate models have probably underestimated the effects of climate change on extreme weather events such as the devastating events [the summer of] 2018, and they will be the future growth of these events
Despite this sobering evidence and growing public recognition of the problem, the current federal administration continues to push for climate change and implement policies that are weakening. Environmental measures are strengthening fossil fuels and ultimately slowing international progress in achieving them the objectives of the Paris Agreement. In fact, Trump's government officials have attempted to discredit some of the most stringent climate sciences – the National Climate Assessment, which is based on the work of more than a dozen federal agencies – as "alarming" or "radical." The White House spokeswoman, Sarah Huckabee Sanders, falsely claimed that the rating was based only on the "most extreme" emissions scenario.
"Trump and the lobbyists and supporters of fossil fuels who run his government have done everything they can to deny science buried government reports, warn of the repercussions and reverse previous measures aimed at reducing carbon dioxide emissions and reversing their carbon footprint Stabilizing warming below dangerous levels, "writes Mann. "In this sense – that is, from a political point of view, yes – we experience a worst-case scenario."
In fact, it is becoming increasingly clear that the worst-case climate arises without immediate and drastic action. Scenario is becoming the rule rather than the exception.
"We are already in a situation where there are very serious consequences for what we have done in the atmosphere," says Bevis, "but the longer we wait, the worse the consequences will be."