Yesterday, the New York Times published the final draft of a broad-based U.S. climate change report. And given the fact that the Trump Administration, brimming with politically-contrived climate change denial, is still pushing full steam toward a reckless withdraw from the Paris Climate Summit, we’re pretty confident that it’s hot information they don’t want you to get your hands on.
The report carries with it a monumental scientific gravitas. A level of credibility that Trump, even in his wildest fantasies, couldn’t hope to achieve. It includes a culmination of research coming from thousands of peer-reviewed studies resulting in the accumulated work of tens of thousands of scientists. The National Oceanic and Atmospheric Administration (NOAA) served as the lead government agency conducting the report. Representatives from three other federal agencies joined with NOAA along with a team of 54 scientist authors and reviewers drawing from both public and private sector institutional knowledge in compiling the report.
The 673 page report represents a massive body of the latest scientific findings on climate change. It includes numerous key advances in understanding which we will take a shot at briefly highlighting for you here.
Humans Are the Primary Cause of Warming by a Huge Margin
The key finding of the report is that humans are causing the Earth to warm very rapidly. The study noted a 95 to 100 percent likelihood that human activity produced the approximate 0.85 C warming since the mid 20th Century and the 0.7 C warming since 1986. For the U.S., the report finds that recent decades have been warmer than any time within the last 1500 years. Meanwhile, it forecasts that future decades will at least be the warmest experienced in tens of thousands to millions of years.
(Tens of thousands of climate scientists agree — the considerable warming trend we’ve seen since the 1880s has been caused by human emissions. Image source: Climate Report.)
The report goes on to state that there is no convincing line of scientific evidence that provides a cause for this warming other than human emissions. That the increasingly accurate observations of solar and volcanic activity reveal only very minor nudges to the climate system compared to the vast heat-trapping influence of human-emitted greenhouse gasses. Meanwhile, though natural variability influences like El Nino and La Nina have effects on climate over months and years, the global impact of these natural sources greatly diminish over the course of the decades long warming regime that is now well established.
Future Warming is Locked in, But it Can be Dramatically Reduced by Cutting Carbon Emissions
Overall, the future isn’t looking too good. Because of past and current human emissions (coal, oil, and gas burning), the report finds that global climate change is projected to continue throughout this Century and beyond. Rapid cuts to greenhouse gas emissions, according to the study, were needed to have a chance of limiting warming to 2 C this Century. But the study found that even an immediate stabilization at present levels of atmospheric greenhouse gasses by ceasing present emissions would result in 0.6 C additional warming compared to recent decades. Longer term, the study points to a necessity that atmospheric CO2, methane, and other greenhouse gasses fall below present levels to meet the goals of preventing 2 C warming over the long term.
Continued emissions result in considerably more warming, according to the study, with temperatures hitting as high as 5 C or more above 1901 to 1960 averages if policies like Trump’s result in renewed increases in fossil fuel burning. What this means is that we can considerably limit the amount of damage caused by human-forced climate change if we rapidly cut emissions in the near term. But if we fail to do that, and Trump is leading us down this more dangerous path by killing the Clean Power Plan and backing out of the Paris Climate Summit, then temperatures will rise into extraordinarily hot and harmful ranges.
The study finds with high confidence that we presently remain on the higher emissions scenario pathways excepting a pause in emissions increases during 2014 and 2015. The study also finds that present rates of greenhouse gas emissions reductions are not yet in line with the goals of the Paris Climate Accord.
Extreme Weather is Becoming More Common and More Attributable to Human Caused Climate Change
Perhaps the most important new takeaway from the report is a developing clearer view of the impact of present warming on severe weather events. The report finds that many temperature and precipitation extremes are becoming more common. That the number of high temperature records over the past twenty years greatly exceeds the number of low temperature records. And that heavy precipitation events have increased in both frequency and intensity. Much evidence has been found for a human-caused influence on soil moisture deficits due to evaporation that leads to more rapid drought intensification. And the incidence of large fires in the Western United States has increased significantly since the 1980s and is expected to increase further.
The study also finds that Northern Hemisphere snow cover and water held in snow has declined. That there has been a decrease in snowstorm frequency along the southern margins of snowy areas. That the Arctic is losing more than 3.5 percent of its sea ice coverage every decade and that September sea ice extent is declining by more than 10 percent per decade. That Arctic land ice losses are also accelerating. It notes a contested scientific linkage between the increased severity of winter storms and a rapid observed warming in the Arctic. The study also identifies changes in tornado frequency and notes a possible linkage between thunderstorm wind intensity, increased convection, hail and climate change. Moreover, the study finds a global intensification of thunderstorms overall as the world has warmed. Tropical cyclone peak intensity is expected to ramp up even as typical cyclone formation regimes are altered.
Perhaps more disturbing is the fact that the study identifies an emerging understanding that human-caused climate change is starting to affect larger natural variability based systems like El Nino, the North Atlantic Oscillation, the North Pacific Oscillation, the Pacific North American Pattern, the Jet Stream, the size of the Tropics, atmospheric circulation patterns, rivers of moisture and storm tracks to varying degrees and with varying degrees of certainty or uncertainty. These systems not only play a major role in present global weather patterns, but our understanding of how they operate is also critical to our ability to predict weather. So climate change based alterations in these larger systems creates higher levels of uncertainty with regards to extreme weather risks.
The key takeaway of all this being that:
Some extremes have already become more frequent, intense, or of longer duration, and many extremes are expected to increase or worsen, presenting substantial challenges for built, agricultural, and natural systems.
Harmful Impacts to Oceans are on the Rise
Oceans, another key aspect of the health of the Earth’s life support system, according to the study, are warming, rising, becoming more acidic, and risk becoming stratified as they lose oxygen.
The study found that the oceans have absorbed 93 percent of the excess heat produced by human greenhouse gas emissions. That this added heat is having a number of serious effects. For one, the rate of sea level rise was found to be faster than at any time in the past 2,800 years. That end Century projections for sea level rise are heavily dependent on future emissions and range from 1 to 8 feet in the study.
The study finds that even present rates of sea level rise have resulted in significant increases in the incidence of coastal flooding. That tidal flooding events has multiplied by 5-10 times the rate observed in the 1960s overall and that the vulnerable Atlantic and Gulf coasts have seen an increase in tidal flooding that is now 25 times times 1960s values due to warming-related sea level rise. As sea level rise accelerates this Century, flooding is expected to considerably worsen — with the most damaging effects happening alongside the highest levels of possible future greenhouse gas emissions. The study also identified potentially compounding effects from possibly worsening Atlantic storms and heavier coastal rainfall events.
Ocean warming and increasing glacial outflows also have a potential to effect ocean overturning circulation in the upper middle latitudes. Of particular interest is the possible disruption of the Atlantic Meridional Overturning Circulation (AMOC) this Century. Recent unconfirmed scientific observation has already pointed to some impacts to AMOC due to warming during recent years. But the report notes that it is presently difficult to validate these observations. Disruption to AMOC would have a considerable impact on North Atlantic weather patterns. It would also reduce both ocean carbon and heat uptake due to a more stratified and less well mixed ocean system. The study identifies a weakening of AMOC of between 12 and 54 percent under worst-case greenhouse gas emissions scenarios.
As risks of ocean stratification mount, acidification of the world’s waters is rapidly increasing. Atmospheric carbon dioxide rising above 400 parts per million was found to worsen detrimental effects by increasing ocean acidity levels. The study found that the rate of ocean acidification increase was unparalleled in the past 66 million years at least. That higher rates of fossil fuel burning and greenhouse gas emissions would result in another doubling or more of ocean acidity by the end of this Century.
Heating, stratifying, and more acidic oceans are also steadily losing oxygen. The study finds that the amount of oxygen held in the oceans is falling coincident with warming. The study identifies a declining ocean oxygen content at intermediate depths and major losses in oxygen in inland seas, estuaries, along coasts, and in parts of the open ocean. Lower oxygen means more ocean dead zones and more toxic anaerobic microbial blooms. Overall ocean oxygen content is expected to fall by 3.5 percent under worst case warming and fossil fuel emissions scenarios by 2100.
Serious Risk of Unanticipated Changes
The level of evidence provided by the study that humans are changing the climate and that these changes are increasingly harmful is mountainous. And this base fact alone is reason enough for a climate change denying Trump Administration to try and bury its findings. But it is perhaps the study’s own admitted uncertainty over future risks that reveals how reckless Trump’s combined denial of climate change and doubling down on fossil fuel based emissions has ultimately become.
The study itself is based on physical model and consensus science findings. This lends weight to the evidence it has provided in that it is highly qualified. However, the study responsibly indicates the potential weak points of model based consensus studies. Models are notably less able to duplicate higher paleoclimate levels of warming — indicating an increased likelihood that rates of warming will be more intense than expected and a reduced likelihood that warming will be less intense than expected. The study also cautions that there is another limitation to the ultimate accuracy of model predictions in that models themselves are unable to capture what it calls critical threshold and compound events.
Compound events are described as multiple extreme climate change events occurring at the same time to generate an unanticipated level of harmful disruption. A good example of a compound event is extreme heat risking injury or loss of life, extreme drought harming crops and water supplies in the same region, and both coinciding with a severe or unprecedented wildfire outbreak. Critical threshold events occur when the climate system crosses a tipping point and then radically adjusts to a new climate state. A worrisome critical threshold event is crossing a tipping point in which significant carbon feedbacks from the Earth System occur — locking in more extreme warming and generating periods in which global temperatures more rapidly spike. Both of these kinds of events have the potential to produce consequences that are difficult or impossible to manage. And the chance of such catastrophic events occurring increases along with higher rates of fossil fuel burning and coinciding higher levels of warming.
The precautionary principle alone demands that we do our best to avoid increasing these uncertain risks even as we steer away from the much more certain harms like sea level rise and generally increasing extreme weather. The science has again given us a more clear, more refined, gift in the form of this very valuable provision of foresight. And yet the current U.S. executive leadership is bound and determined to obstinately ignore or it, cast doubt on it, and do everything possible to cloud the clear and priceless message being sent to us by an army of selfless and dedicated climate researchers.
Images taken directly from the report
Hat tip to Greg
Hat tip to Wili