Even if all fossil fuel emissions are eradicated, if current rates of deforestation in the tropics continue through to 2100 then there will still be a 1.5 degree Celsius increase in global temperature
While carbon dioxide emissions from energy use must be the primary target of climate change mitigation efforts, land use and land cover change (LULCC) also represent an important source of climate forcing.
Tackling deforestation should be higher on the climate change agenda.
In the fight against climate change, much of the focus rests on reducing our dependence on fossil fuels and developing alternative energy sources. However, the results of a new study suggest that far more attention should be paid to deforestation and how the land is used subsequently – the effects of which make a bigger contribution to climate change than previously thought.
The research, conducted by Cornell University and published in the journal Environmental Research Letters,shows just how much this impact has been underestimated. Even if all fossil fuel emissions are eradicated, if current rates of deforestation in the tropics continue through to 2100 then there will still be a 1.5 degree Celsius increase in global temperature….
Abstract: While carbon dioxide emissions from energy use must be the primary target of climate change mitigation efforts, land use and land cover change (LULCC) also represent an important source of climate forcing. In this study we compute time series of global surface temperature change separately for LULCC and non-LULCC sources (primarily fossil fuel burning), and show that because of the extra warming associated with the co-emission of methane and nitrous oxide with LULCC carbon dioxide emissions, and a co-emission of cooling aerosols with non-LULCC emissions of carbon dioxide, the linear relationship between cumulative carbon dioxide emissions and temperature has a two-fold higher slope for LULCC than for non-LULCC activities. Moreover, projections used in the Intergovernmental Panel on Climate Change (IPCC) for the rate of tropical land conversion in the future are relatively low compared to contemporary observations, suggesting that the future projections of land conversion used in the IPCC may underestimate potential impacts of LULCC. By including a “business as usual” future LULCC scenario for tropical deforestation, we find that even if all non-LULCC emissions are switched off in 2015, it is likely that 1.5°C of warming relative to the preindustrial era will occur by 2100. Thus, policies to reduce LULCC emissions must remain a high priority if we are to achieve the low to medium temperature change targets proposed as a part of the Paris Agreement. Future studies using integrated assessment models and other climate simulations should include more realistic deforestation rates and the integration of policy that would reduce LULCC emissions.
With each passing year, the odds get worse that climate change mitigation efforts will be able to stave off catastrophic warming of more than 2 degrees Celsius, or 3.6 degrees Fahrenheit.
A new study published on July 31 in Nature Climate Change is the opposite of reassuring when it comes to this math. Using statistical tools, the authors found that there’s a 5% chance Earth will warm 2 degrees or less by the end of this century and a 90% chance that temperatures will increase from 2.0 to 4.9°C if historical trends continue unabated. The other 5%, well that’s worst-case scenario runaway global warming—the kind of thing that keeps geoengineers up at night.
As for the ambitious 1.5°C target included in the Paris Agreement, there’s apparently only a 1% chance of meeting that (not so surprising considering the planet has already warmed 1°C since pre-industrial times). So as climate change deniers like President Trump, EPA chief Scott Pruitt, and many GOP lawmakers put their money on taking little to no action and somehow escaping devastating warming, in truth it will take a herculean global effort to avoid costly and harmful impacts.
The reality of human-caused climate change is increasingly clear for anyone to see. Last year was the hottest year on record, and the 12 warmed years on record have all occurred since 1998. 2017 is on track to be the second-warmest year on record; and this even in the absence of an El Niño warming event like 2016’s. According to NASA, the first six months of this year were 0.94°C above the 1950–1980 average…
…Adrian Raftery, a UW professor of statistics and sociology and lead author on the new study, said while their analysis is compatible with previous estimates, it shows “we’re closer to the margin than we think….The goal of 2 degrees is very much a best-case scenario,” said Raftery in a statement. “It is achievable, but only with major, sustained effort on all fronts over the next 80 years.”
…Richard Startz, an economist at the University of California at Santa Barbara who worked on the study, told Project Earth the most surprising finding was that population growth will not be a major factor in increased CO2 emissions over the course of the century. This is in large part because most of that growth will occur in Africa, where per capita emissions will remain relatively low.
What matters a lot more for future warming is actually carbon intensity. According to the study, even though carbon intensity has dropped in recent decades as countries increase energy efficiency and enact carbon-reducing policies, it will need to drop much more to see the kind of progress the global climate community is aiming for with the Paris Agreement targets.
“Our study already assumes that the trends in carbon intensity will continue to improve,” said Startz. “So more reductions in carbon intensity aren’t enough. We need much faster reductions in carbon intensity than we’ve already been seeing.”
Startz said in his opinion there are two primary ways to accomplish this: Financial incentives to reduce carbon emissions—like carbon taxes or cap-and-trade programs—and a lot more support for scientific research that would help reduce emissions. “For example, the invention of practical LED lighting has been a small but significant achievement in reducing energy needs,” he said. “If someone could greatly increase battery cost-effectiveness, that would buy us a lot.”
Even if we meet our most ambitious climate goal — keeping global temperatures within a strict 1.5 degrees Celsius (or 2.7 degree Fahrenheit) of their preindustrial levels — there will still be consequences, scientists say. And they’ll last for years after we stop emitting carbon dioxide into the atmosphere.
New research suggests that extreme El Niño events — which can cause intense rainfall, flooding and other severe weather events in certain parts of the world — will occur more and more often as long as humans continue producing greenhouse gas emissions. And even if we’re able to stabilize the global climate at the 1.5-degree threshold, the study concludes, these events will continue to increase in frequency for up to another 100 years afterward. The findings were published Monday in the journal Nature Climate Change.
“It was really a surprise that what we find is after we reach 1.5 degrees Celsius and stabilize world temperatures, the frequency of extreme El Niño continued to increase for another century,” said Wenju Cai, a chief research scientist at Australia’s Commonwealth Scientific and Industrial Research Organization and one of the study’s lead authors. “We were expecting that the risk would stabilize.” …
…The models suggested that by the time we hit the 1.5-degree mark, the frequency of extreme El Niño will have doubled from its preindustrial level of about five events every 100 years to about 10. This increase will occur steadily over time, the researchers note, meaning that any additional increase in carbon dioxide in the future will lead to an increased risk of an extreme event…
…The researchers noted that the same results did not hold true for La Niña events, which often produce the opposite effects of El Niño. While previous research has suggested that more intense warming scenarios may lead to more frequent La Niña events as well, the milder climate trajectory in this study did not produce any significant changes.
Trenberth, who was not involved with the research, still has concerns about the models used in the research, which he says are “the same flawed models used before.” He argues that the models do a poor job of capturing some of the impacts of El Niño events — even “regular” ones — and the way they’re influenced by temperature and moisture in the atmosphere….
Atmospheric CO2 should be reduced to less than 350 parts per million (ppm) from its present level of about 400 ppm
Reduction of CO2 below 350 ppm will cause temperature to peak and slowly decrease to about +1°C later this century. This goal requires negative CO2 emissions, that is, extracting CO2 from the air, in addition to rapid phase-down of fossil fuel emissions.
Reforestation and improved agricultural practices could remove 2/3 of atmospheric CO2 required to get to 350 ppm if start 6% CO2 reductions annually by 2021- relatively inexpensive and have added benefits such as improved soil fertility and forest products
Reducing greenhouse-gas emissions is not enough to limit global warming to a level that wouldn’t risk young people’s future, according to a new study by scientists who say we need negative emissions. Measures such as reforestation could accomplish much of the needed CO2 removal from the atmosphere, but continued high fossil fuel emissions would demand expensive technological solutions to extract CO2 and prevent dangerous warming….
….”We show that a target of limiting global warming to no more than +2°C relative to pre-industrial levels is not sufficient, as +2°C would be warmer than the Eemian period, when sea level reached +6-9 metres relative to today,” says Hansen. The Eemian ended some 115,000 years ago and was a warm period in the Earth’s history between two glacial ages.
The danger, according to the Earth System Dynamics study, is that a long-term global average temperature of +2°C — or even of +1.5°C, the other temperature limit discussed in the 2015 Paris Agreement — could spur ‘slow’ climate feedbacks. In particular, it could lead to partial melting of the ice sheets, which would result in a significant increase in sea-level rise as happened in the Eemian …
The Hansen-led team says that atmospheric CO2 should be reduced to less than 350 parts per million (ppm) from its present level of about 400 ppm.Global average temperature reached +1.3°C above pre-industrial levels in 2016 and will increase at least a few tenths of a degree more during the next few decades because of the delayed response to past increases in CO2 and other gases. Reduction of CO2 below 350 ppm will cause temperature to peak and slowly decrease to about +1°C later this century. This goal requires negative CO2 emissions, that is, extracting CO2 from the air, in addition to rapid phase-down of fossil fuel emissions.
….The team estimates that, if we start reducing CO2 emissions in 2021 at a rate of 6% a year, we’d need to also extract about 150 gigatonnes of carbon from the atmosphere by 2100. Most of this, about 100 gigatonnes, could come from improved agricultural and forestry practices alone. These measures can be relatively inexpensive and have added benefits such as improved soil fertility and forest products…
….However, if CO2 emissions grow at a rate of 2% a year (between 2000 and 2015 they rose on average 2.6% a year), we’d need to extract well over 1000 gigatonnes of carbon from the atmosphere by 2100. This could only be achieved with a costly technological solution, capable of sucking carbon from the atmosphere.….. The team estimates that the total cost of this technology could be up to 500 trillion euros, or about 535 [trillion] US dollars. They also point out that extraction technologies have “large risks and uncertain feasibility.”…
James Hansen, Makiko Sato, Pushker Kharecha, Karina von Schuckmann, David J. Beerling, Junji Cao, Shaun Marcott, Valerie Masson-Delmotte, Michael J. Prather, Eelco J. Rohling, Jeremy Shakun, Pete Smith, Andrew Lacis, Gary Russell, Reto Ruedy. Young people’s burden: requirement of negative CO2 emissions. Earth System Dynamics, 2017; 8 (3): 577 DOI: 10.5194/esd-8-577-2017
The longer humans continue to pour carbon dioxide into the atmosphere, the closer we draw to leaving the next generation with an unmanageable climate problem, scientists say. A new study, [see above] just out Tuesday in the journal Earth System Dynamics, suggests that merely reducing greenhouse gas emissions may no longer be enough — and that special technology, aimed at removing carbon dioxide from the atmosphere, may also be necessary to keep the Earth’s climate within safe limits for future generations.The research was largely inspired by a landmark climate change lawsuit brought by 21 children against the federal government, which is scheduled to go to trial in February 2018, and will be used as scientific support in the case. In fact, its lead author, Columbia University climatologist and former NASA scientist James Hansen, is a plaintiff on the case, along with his now 18-year-old granddaughter.The new paper argues that the Paris Agreement’s target of keeping global temperatures within 1.5 to 2 degrees Celsius (2.7 to 3.6 degrees Fahrenheit) of their preindustrial levels isn’t strong enough. During a previous warm period in the Earth’s history, known as the Eemian, or the last interglacial period, the planet experienced similar levels of warming, the authors note — and the resulting consequences included the disintegration of ice sheets and six to nine meters of sea level rise…….the paper calls for a more stringent target of bringing atmospheric carbon dioxide levels down from their current concentration of more than 400 parts per million to about 350 parts per million by the end of the century. This would bring global temperature closer to a 1-degree threshold, rather than 1.5 or 2 degrees, the authors say……..But the study has already come in from some criticism from other scientists, such as Kevin Trenberth of the National Center for Atmospheric Research, who told The Washington Post that some aspects of the study were “alarmist” and that if changes come slowly enough, society will be able to adapt to them. Trenberth said he disagreed that the 1 degree target is justified and thinks that even 1.5 degrees is “unrealistic.”……Other researchers are a little more cautiously accepting of the paper’s points.Cristian Proistosescu, a postdoctoral researcher at the University of Washington who was not involved with the new research (but who recently led a major study, himself, on the potential future impact of slow-developing climate modes) expressed some skepticism about using the Earth’s ancient history as an analogy for the future. He noted that some of the conditions that were true during the Eemian — the existence of large ice sheets that have already disappeared, for instance — are not the same now. And because humans have not been around to witness some of the slow-developing climate processes that scientists fear will intensify in the future, there’s uncertainty about how and even whether they will affect future climate change.“But that would be the wrong way to think about it,” he added in an email to The Post. “The more important point is that we cannot rule out the very real probability that there are slow feedbacks — and risk is probability times cost. … Once you start thinking in terms of risks I would concur with Dr. Hansen that the current trajectory presents some unacceptable risks.”…
One of the world’s most famous climate scientists has just calculated the financial burden that tomorrow’s young citizens will face to keep the globe at a habitable temperature and contain global warming and climate change – a $535 trillion bill. Climate News Network, United Kingdom.
Former UN climate chief Christiana Figueres among signatories of letter warning that the next three years will be crucial to stopping the worst effects of global warming
6 goals for 2020– increasing renewable energy to 30% of electricity use; plans from leading cities and states to decarbonise by 2050; 15% of new vehicles sold to be electric; and reforms to land use, agriculture, heavy industry and the finance sector, to encourage green growth…..
Avoiding dangerous levels of climate change is still just about possible, but will require unprecedented effort and coordination from governments, businesses, citizens and scientists in the next three years, a group of prominent experts has warned.
But while temperatures have risen, global carbon dioxide emissions have stayed broadly flat for the past three years. This gives hope that the worst effects of climate change – devastating droughts, floods, heatwaves and irreversible sea level rises – may be avoided, according to a letter published in the journal Nature this week.
…..They calculate that if emissions can be brought permanently lower by 2020 then the temperature thresholds leading to runaway irreversible climate change will not be breached….They set out six goals for 2020 which they said could be adopted at the G20 meeting in Hamburg on 7-8 July.
To prioritize actions, we’ve identified milestones in six sectors….These goals may be idealistic at best, unrealistic at worst. However, we are in the age of exponential transformation and think that such a focus will unleash ingenuity. By 2020, here’s where the world needs to be:
Energy. Renewables make up at least 30% of the world’s electricity supply — up from 23.7% in 2015 (ref. 8). No coal-fired power plants are approved beyond 2020, and all existing ones are being retired.
Infrastructure. Cities and states have initiated action plans to fully decarbonize buildings and infrastructures by 2050, with funding of $300 billion annually. Cities are upgrading at least 3% of their building stock to zero- or near-zero emissions structures each year9.
Transport. Electric vehicles make up at least 15% of new car sales globally, a major increase from the almost 1% market share that battery-powered and plug-in hybrid vehicles now claim. Also required are commitments for a doubling of mass-transit utilization in cities, a 20% increase in fuel efficiencies for heavy-duty vehicles and a 20% decrease in greenhouse-gas emissions from aviation per kilometre travelled.
Land. Land-use policies are enacted that reduce forest destruction and shift to reforestation and afforestation efforts. Current net emissions from deforestation and land-use changes form about 12% of the global total. If these can be cut to zero next decade, and afforestation and reforestation can instead be used to create a carbon sink by 2030, it will help to push total net global emissions to zero, while supporting water supplies and other benefits. Sustainable agricultural practices can reduce emissions and increase CO2 sequestration in healthy, well-managed soils.
Industry. Heavy industry is developing and publishing plans for increasing efficiencies and cutting emissions, with a goal of halving emissions well before 2050. Carbon-intensive industries — such as iron and steel, cement, chemicals, and oil and gas — currently emit more than one-fifth of the world’s CO2, excluding their electricity and heat demands.
Finance. The financial sector has rethought how it deploys capital and is mobilizing at least $1 trillion a year for climate action. Most will come from the private sector. Governments, private banks and lenders such as the World Bank need to issue many more ‘green bonds’ to finance climate-mitigation efforts. This would create an annual market that, by 2020, processes more than 10 times the $81 billion of bonds issued in 2016.
….While the greenhouse gases poured into the atmosphere over the last two centuries have only gradually taken effect, future changes are likely to be faster, scientists fear.
Christiana Figueres, Hans Joachim Schellnhuber, Gail Whiteman, Johan Rockström, Anthony Hobley & Stefan Rahmstorf. Three years to safeguard our climate. Nature 546, 593–595 () doi:10.1038/546593a
What appears to be a recent change to a positive phase of the Interdecadal Pacific Oscillation is likely to accelerate global warming, breaking through the agreed Paris target of 1.5°C by as early as 2026.
Since 1999, the IPO has been in a negative phase but consecutive record-breaking warm years in 2014, 2015 and 2016 have led climate researchers to suggest this may have changed. In the past, these positive phases have coincided with accelerated global warming.
“Even if the IPO remains in a negative phase, our research shows we will still likely see global temperatures break through the 1.5°C guardrail by 2031,” said lead author Dr Ben Henley. “If the world is to have any hope of meeting the Paris target, governments will need to pursue policies that not only reduce emissions but remove carbon from the atmosphere.”
“Should we overshoot the 1.5°C limit, we must still aim to bring global temperatures back down and stabilise them at that level or lower.”..In the past, we have seen positive IPOs from 1925-1946 and again from 1977-1998. These were both periods that saw rapid increases in global average temperatures. The world experienced the reverse — a prolonged negative phase — from 1947-1976, when global temperatures stalled….
Dr Henley said…”Policy makers should be aware of just how quickly we are approaching 1.5°C. The task of reducing emissions is very urgent indeed.”
Benjamin J. Henley, Andrew D. King. Trajectories toward the 1.5°C Paris target: Modulation by the Interdecadal Pacific Oscillation. Geophysical Research Letters, 2017; DOI: 10.1002/2017GL073480
Arctic sea ice may vanish in summers this century even if governments achieve a core target for limiting global warming set by almost 200 nations in 2015, scientists said on Monday. …Under the 2015 Paris Agreement, governments set a goal of limiting the rise in average world temperatures to well below 2 degrees Celsius (3.6 Fahrenheit) above pre-industrial times, with an aspiration of just 1.5C (2.7F).
“The 2 degrees Celsius target may be insufficient to prevent an ice-free Arctic,” James Screen and Daniel Williamson of Exeter University in Britain wrote in the journal Nature Climate Change after a statistical review of ice projections.
A 2C rise would still mean a 39 percent risk that ice will disappear in the Arctic Ocean in summers, they said. Ice was virtually certain to survive, however, with just 1.5C of warming.And they said they estimated a 73 percent probability that the ice would disappear in summer unless governments make deeper cuts in emissions than their existing plans. They estimated temperatures will rise 3C (5.4F) on current trends….
2016 is about to cap off the hottest year on record for the third straight year, a remarkable streak fueled primarily by the excess heat trapped in Earth’s atmosphere by ever-rising levels of greenhouse gases. While that streak is expected to end, in part because of the demise of one of the strongest El Niños on record, 2017 is still expected to be among the hottest years in more than 130 years of record keeping, according to a forecast from the U.K. Met Office…..Because of global warming, 16 of the 17 hottest years on record have occurred this century, the only exception being the strong El Niño year of 1998….
The U.K. Met Office’s forecast for 2017’s global annual average temperature. Credit: Met Office
… The running average of global temperatures throughout 2016 compared to recent years. Each month shows the average of that month’s temperature and each month before it. …
The head of the United Nation’s climate body has called for a thorough assessment of the feasibility of the international goal to limit warming to 1.5C.
Dr Hoesung Lee, chair of the Intergovernmental Panel on Climate Change (IPCC), told delegates at a meeting in Geneva, which is designed to flesh out the contents of a special report on 1.5C, that they bore a “great responsibility” in making sure it meets the expectations of the international climate community.
To be policy-relevant, the report will need to spell out what’s to be gained by limiting warming to 1.5C, as well as the practical steps needed to get there within sustainability and poverty eradication goals.
More than ever, urged Lee, the report must be easily understandable for a non-scientific audience. The IPCC has come under fire in the past over what some have called its “increasingly unreadable” reports….