New analysis of 40 years’ worth of satellite data shows that it’s a near-certainty that humanity is actively causing global climate change.
Climate deniers often claim, in the face of overwhelming evidence, that the planet is heating up and natural disasters are becoming more intense and common just because that’s the way it is – incorrectly insisting that humanity’s love affair with fossil fuels has nothing to do with it.
Now, scientists say the chances that that’s true are just one in a million.
According to the research by scientists at California’s Lawrence Livermore National Laboratory, that’s because climate data has now reached a so-called “gold standard” of scientific evidence – there’s only a one in a million chance that ongoing climate change could have been caused by anything other than humanity, reports Reuters.
“The narrative out there that scientists don’t know the cause of climate change is wrong,” Benjamin Santer, the scientist who led the research, told Reuters. “We do.” The scientific research process almost never eradicates uncertainty: researchers test their hypotheses to get a better understanding of the world, but there’s almost always some other factor out there that could have impacted their findings.
In other words, a gold standard is not something that’s taken lightly.
The new analysis looked at the three largest satellite data sets used by climate scientists. It shows that two of those data sets reached the gold standard of certainty that humanity causes climate change back in 2005, and the third did in 2016.
That level of certainty, highly uncommon in scientific research, makes humanity’s impact on the planet very clear. And now we have to figure out what to do about it.
“Humanity cannot afford to ignore such clear signals,” reads the analysis.
“There’s a one-in-a-million chance humans are NOT warming the planet.” The Nature Climate Change study also comes on the heels of reports that the melting of ice in Antarctica and the warming of the ocean are both occurring much faster than previously thought; that the last four years have been the hottest on record; and that the warming of the globe could cause clouds to disappear from the sky in the next generation, leading to an 8º Celsius (14.4º Fahrenheit) jump in temperature. “Humanity cannot afford to ignore such clear signals,” the authors of the most recent study wrote in Nature Climate Change.
Most Americans now recognize the scientific community’s consensus that human activity is fueling the climate crisis, according to polls—but for those who are still unconvinced of the conclusion reached by 97 percent of climate scientists, a new study makes an even more definite assertion.
Scientists at the Lawrence Livermore National Laboratory in California found that the information available can now be classified as “five-sigma”—a standard in the scientific community meaning that there is a one-in-a-million chance that the same data would be observable if humans were not causing the planet to grow warmer through activities like fossil fuel extraction. The classification represents a “gold standard” level of certainty.
“The narrative out there that scientists don’t know the cause of climate change is wrong,” Benjamin Santer, who led the study, told Reuters. “We do.”
Scientists applied the same “five-sigma” measure to research confirming the existence of the Higgs boson subatomic particle in 2012, a finding that was received with applause from the science community and the press.
The report, which was published in the journal Nature Climate Change, builds on the United Nations’ Intergovernmental Panel on Climate Change (IPCC) report from 2013, which found that it was “extremely likely” that humans were causing the climate crisis—with a 95 percent chance.
In recent years, although President Donald Trump and other Republican lawmakers have attempted to cast doubt on the scientific consensus that human activity is causing global warming and the climate crisis, the American public has increasingly believed scientists.
In a 2018 survey by the Yale Program on Climate Change Communication, 62 percent of Americans believed that man-made climate change was taking place, versus just 47 percent convinced that was the case just five years earlier.
The Nature Climate Change study also comes on the heels of reports that the melting of ice in Antarctica and the warming of the ocean are both occurring much faster than previously thought; that the last four years have been the hottest on record; and that the warming of the globe could cause clouds to disappear from the sky in the next generation, leading to an 8º Celsius (14.4º Fahrenheit) jump in temperature.
“Humanity cannot afford to ignore such clear signals,” the authors of the most recent study wrote in Nature Climate Change.
Ice-free Arctic summers could happen on earlier side of predictions: A new study in AGU’s journal Geophysical Research Letters predicts the Arctic Ocean will be ice-free in summer by mid-century. Science Daily and The American Geophysical Union, February 27, 2019
Computer models predict climate change will cause the Arctic to be nearly free of sea ice during the summer by the middle of this century, unless human greenhouse gas emissions are greatly reduced.
But a closer examination of long-term temperature cycles in the tropical Pacific points towards an ice-free Arctic in September, the month with the least sea ice, on the earlier side of forecasts, according to a new study in the AGU journal Geophysical Research Letters.
“The trajectory is towards becoming ice-free in the summer but there is uncertainty as to when that’s going to occur,” said James Screen, an associate professor in climate science at the University of Exeter in the U.K. and the lead author of the new study.
There are different climate models used by researchers to predict when the first ice-free Arctic September will occur. Most models project there will fewer than 1 million square kilometers of sea ice around the middle of this century, but projections of when that will occur vary within 20-year windows due to natural climate fluctuations.
The climate model used in the new study predicts an ice-free Arctic summer sometime between 2030 and 2050, if greenhouse gases continue to rise.
By accounting for a long-term warming phase in the tropical Pacific, the new research shows an ice-free Arctic is more likely to occur on the earlier side of that window, closer to 2030 than 2050.
Long-term temperature changes
Ocean temperatures in the Pacific always vary from month-to-month and from year-to-year, but slowly evolving ocean processes cause long-term temperature shifts lasting between 10 and 30 years. These shifts in temperature, known as the Interdecadal Pacific Oscillation (IPO), translate into an approximately 0.5 degree Celsius (0.9 degree Fahrenheit) shift in ocean surface temperature in the tropics over the 10- to 30-year cycle.
Around five years ago, the Pacific began to switch from the cold to warm phase of the IPO. Screen and his co-author plotted predictions of when an ice-free Arctic would occur in model experiments where the IPO was shifting in the same direction as the real world. They compared these to predictions where the IPO was moving in the opposite direction, that is, switching from a warm to cold phase.
They found model predictions that were in sync with actual conditions showed an earlier ice-free Arctic, by seven years on average, than those predictions that were out of step with reality.
Screen says these results need to be interpreted as part of a bigger picture. Human-caused climate change is the main reason for sea ice loss, so the timing of the first ice-free summer will also depend considerably on whether greenhouse gas emissions continue to rise or are curtailed. But the new results do suggest that we are more likely to see an ice-free September on the earlier side of the 20-year window of predictions.
“You can hedge your bets,” he said. “The shift in the IPO means there’s more chance of it being on the earlier end of that window than on the later end.”
Alexandra Jahn, an assistant professor in atmospheric and oceanic studies at the University of Colorado Boulder who was not involved in the new study, said the paper is very interesting and will likely inspire more research.
“The finding that we may be able to use the IPO phase to narrow the uncertainty range of over 20 years of when we may first see an ice-free Arctic Ocean in September is very promising,” she said.
Jennifer Kay, an assistant professor in environmental science at the University of Colorado Boulder who was also not involved in the new research, said the study “is an important advance in our understanding of regional Arctic sea ice loss, the chaotic nature of ice loss, and the connections between Arctic sea ice loss and extrapolar regions.”
J. A. Screen, C. Deser. Pacific Ocean Variability Influences the Time of Emergence of a Seasonally Ice‐Free Arctic Ocean. Geophysical Research Letters, 2019; DOI: 10.1029/2018GL081393
Carolina Voigt, Maija E. Marushchak, Mikhail Mastepanov, Richard E. Lamprecht, Torben R. Christensen, Maxim Dorodnikov, Marcin Jackowicz-Korczyński, Amelie Lindgren, Annalea Lohila, Hannu Nykänen, Markku Oinonen, Timo Oksanen, Vesa Palonen, Claire C. Treat, Pertti J. Martikainen, Christina Biasi. Ecosystem carbon response of an Arctic peatland to simulated permafrost thaw. Global Change Biology, 2019; DOI: 10.1111/gcb.14574
Temperatures in the Arctic are rising twice as fast as in the rest of the world, causing permafrost soils to thaw. Permafrost peatlands are biogeochemical hot spots in the Arctic as they store vast amounts of carbon. Permafrost thaw could release part of these long-term immobile carbon stocks as the greenhouse gases carbon dioxide (CO2) and methane (CH4) to the atmosphere, but how much, at which time-span and as which gaseous carbon species is still highly uncertain.
A new study led by researchers from the University of Eastern Finland and the University of Montreal, in cooperation with researchers from various Nordic research institutions, finds that peatlands may strengthen the permafrost-carbon feedback by adding to the atmospheric CO2 burden post-thaw. The study was recently published in Global Change Biology — a leading journal in environmental science.
By applying a novel experimental approach using intact plant-soil systems (mesocosms), the authors were able to simulate permafrost thaw (thawing of the upper 10-15cm of permafrost) under near-natural conditions. Greenhouse gas flux dynamics were monitored via high resolution flow through gas measurements, combined with detailed monitoring of soil greenhouse gas concentration dynamics, yielding insights into gas production and consumption potential of individual soil layers. The study finds that under dry conditions, peatlands may strengthen the permafrost-carbon feedback by adding to the atmospheric CO2burden post-thaw. However, as long as the water table remains low, the results reveal a strong CH4 sink capacity in these types of Arctic ecosystems pre and postthaw, with the potential to compensate for part of the permafrost CO2 losses over longer timescales.
To stabilize the Earth’s climate for people and ecosystems, it is imperative to ramp up natural climate solutions and, at the same time, accelerate mitigation efforts across the energy and industrial sectors, according to a new policy perspective published today in Science. Among their findings, the researchers warn that a ten-year delay in emissions reductions from energy and industry could this century result in emissions that negate the net potential emissions reductions benefit of natural climate solutions.
Christa M. Anderson, Ruth S. Defries, Robert Litterman, Pamela A. Matson, Daniel C. Nepstad, Stephen Pacala, William H. Schlesinger, M. Rebecca Shaw, Pete Smith, Christopher Weber, Christopher B. Field. Natural climate solutions are not enough. Science, 2019; 363 (6430): 933-934 DOI: 10.1126/science.aaw2741