Nature-based solutions such as tree planting, protecting peatlands and better land management could account for 37% of all cuts needed by 2030 to keep global temperature increases below 2C, says study (see GuardianUK article about this study here)
Bronson Griscom et al. Natural Climate Solutions. PNAS (Proceedings of the Ntional Academy of Sciences, US). October 17 2018 doi: 10.1073/pnas.1710465114
Most nations recently agreed to hold global average temperature rise to well below 2 °C. We examine how much climate mitigation nature can contribute to this goal with a comprehensive analysis of “natural climate solutions” (NCS): 20 conservation, restoration, and/or improved land management actions that increase carbon storage and/or avoid greenhouse gas emissions across global forests, wetlands, grasslands, and agricultural lands. We show that NCS can provide over one-third of the cost-effective climate mitigation needed between now and 2030 to stabilize warming to below 2 °C.Alongside aggressive fossil fuel emissions reductions, NCS offer a powerful set of options for nations to deliver on the Paris Climate Agreement while improving soil productivity, cleaning our air and water, and maintaining biodiversity.
Abstract: Better stewardship of land is needed to achieve the Paris Climate Agreement goal of holding warming to below 2 °C; however, confusion persists about the specific set of land stewardship options available and their mitigation potential. To address this, we identify and quantify “natural climate solutions” (NCS): 20 conservation, restoration, and improved land management actions that increase carbon storage and/or avoid greenhouse gas emissions across global forests, wetlands, grasslands, and agricultural lands. We find that the maximum potential of NCS—when constrained by food security, fiber security, and biodiversity conservation—is 23.8 petagrams of CO2 equivalent (PgCO2e) y−1 (95% CI 20.3–37.4). This is ≥30% higher than prior estimates, which did not include the full range of options and safeguards considered here. About half of this maximum (11.3 PgCO2e y−1) represents cost-effective climate mitigation, assuming the social cost of CO2 pollution is ≥100 USD MgCO2e−1 by 2030. Natural climate solutions can provide 37% of cost-effective CO2 mitigation needed through 2030 for a >66% chance of holding warming to below 2 °C. One-third of this cost-effective NCS mitigation can be delivered at or below 10 USD MgCO2−1. Most NCS actions—if effectively implemented—also offer water filtration, flood buffering, soil health, biodiversity habitat, and enhanced climate resilience. Work remains to better constrain uncertainty of NCS mitigation estimates. Nevertheless, existing knowledge reported here provides a robust basis for immediate global action to improve ecosystem stewardship as a major solution to climate change.
From the text:
Our assessment of the potential contribution of NCS to meeting the Paris Agreement is conservative in three ways. First, payments for ecosystem services other than carbon sequestration are not considered here and could spur cost-effective implementation of NCS beyond the levels we identified. Natural climate solutions enhance biodiversity habitat, water filtration, flood control, air filtration, and soil quality (Fig. 1) among other services, some of which have high monetary values (34⇓–36) (see SI Appendix, Table S5 for details). Improved human health from dietary shifts toward plant-based foods reduce healthcare expenses and further offset NCS costs (37).
Second, our findings are conservative because we only include activities and greenhouse gas fluxes where data were sufficiently robust for global extrapolation. For example, we exclude no-till agriculture (Conservation Agriculture pathway), we exclude improved manure management in concentrated animal feed operations (Nutrient Management pathway), we exclude adaptive multipaddock grazing (Grazing pathways), and we exclude soil carbon emissions that may occur with conversion of forests to pasture (Avoided Forest Conversion pathway). Future research may reveal a robust empirical basis for including such activities and fluxes within these pathways.
Third, the Paris Agreement states goals of limiting warming to “well below 2 °C” and pursuing “efforts to limit the temperature increase to 1.5 °C.” Our analysis specifies a >66% chance of holding warming to just below 2 °C (30). Additional investment in all mitigation efforts (i.e., beyond ∼100 USD MgCO2−1), including NCS, would be warranted to keep warming to well below 2 °C, or to 1.5 °C, particularly if a very likely (90%) chance of success is desired.
New study shows we’ve been underestimating nature’s role in tackling climate change
…Forest loss accounts for 8 to 10 percent of carbon emissions globally; tropical rainforests ….work as massive carbon sinks and are home to many of the world’s indigenous people and endangered species. But other global ecosystems and managed lands—from farmlands and peatlands to seagrass and tidal marshes—have garnered less attention from climate regulators, both as a source of emissions and a potential mitigation solution….
66% chance of limiting global temperature increases to below 2C if global energy-related carbon emissions peak by 2020 and fall by more than 70% in the next 35 years
Necessitates “deep decarbonisation” of electricity, tdransport, heat, industrial, forestry and agricultural systems across the world
Rapid changes in electricity, heat, buildings, industry and mobility are needed including tripling of the annual rate of energy efficiency improvement, retrofitting the entire building stock, generating 95% of electricity from low-carbon sources by 2050 and shifting almost entirely towards electric cars.
September 21, 2017 University of Sussex
…To provide a reasonable (66%) chance of limiting global temperature increases to below 2oC, the International Energy Agency and International Renewable Energy Agency suggest that global energy-related carbon emissions must peak by 2020 and fall by more than 70% in the next 35 years. This implies a tripling of the annual rate of energy efficiency improvement, retrofitting the entire building stock, generating 95% of electricity from low-carbon sources by 2050 and shifting almost entirely towards electric cars.
This elemental challenge necessitates “deep decarbonisation” of electricity, transport, heat, industrial, forestry and agricultural systems across the world. But despite the recent rapid growth in renewable electricity generation, the rate of progress towards this wider goal remains slow…
The Policy Forum provides four key lessons for how to accelerate sustainability transitions.
Lesson 1: Focus on socio-technical systems rather than individual elements…Accelerated low-carbon transitions therefore depend on both techno-economic improvements, and social, political and cultural processes…Traditional policy approaches emphasizing a single technology will not be enough…
Lesson 2: Align multiple innovations and systems…accelerated low-carbon transitions in electricity depend not only on the momentum of renewable energy innovations like wind, solar-PV and bio-energy, but also on complementary innovations including energy storage and demand response. These need aligned and then linked so that innovations are harmonized…
Lesson 3: Offer societal and business support…Public support is crucial for effective transition policies. Low-carbon transitions in mobility, agro-food, heat and buildings will also involve millions of citizens who need to modify their purchase decisions, user practices, beliefs, cultural conventions and skills. To motivate citizens, financial incentives and information about climate change threats need to be complemented by positive discourses about the economic, social and cultural benefits of low-carbon innovations….
Lesson 4: Phase out existing systems…Phasing out existing systems accelerates transitions by creating space for niche-innovations and removing barriers to their diffusion. …
Frank W. Geels, Benjamin K. Sovacool, Tim Schwanen, Steve Sorrell. Sociotechnical transitions for deep decarbonization. Science, 2017; 357 (6357): 1242 DOI: 10.1126/science.aao3760
A new study evaluating models of future climate scenarios has led to the creation of the new risk categories ‘catastrophic’ and ‘unknown’ to characterize the range of threats posed by rapid global warming. Researchers propose that unknown risks imply existential threats to the survival of humanity. These categories describe two low-probability but statistically significant scenarios that could play out by century’s end, in [the] new study…
The risk assessment stems from the objective stated in the 2015 Paris Agreement regarding climate change that society keep average global temperatures “well below” a 2°C (3.6°F) increase from what they were before the Industrial Revolution.
Even if that objective is met, a global temperature increase of 1.5°C (2.7°F) is still categorized as “dangerous,” meaning it could create substantial damage to human and natural systems. A temperature increase greater than 3°C (5.4°F) could lead to what the researchers term “catastrophic” effects, and an increase greater than 5°C (9°F) could lead to “unknown” consequences which they describe as beyond catastrophic including potentially existential threats. The specter of existential threats is raised to reflect the grave risks to human health and species extinction from warming beyond 5° C, which has not been experienced for at least the past 20 million years…
…”When we say five percent-probability high-impact event, people may dismiss it as small but it is equivalent to a one-in-20 chance the plane you are about to board will crash,” said Ramanathan. “We would never get on that plane with a one-in-20 chance of it coming down but we are willing to send our children and grandchildren on that plane.”…
….Aggressive measures to curtail the use of fossil fuels and emissions of so-called short-lived climate pollutants such as soot, methane and HFCs would need to be accompanied by active efforts to extract CO2 from the air and sequester it before it can be emitted. It would take all three efforts to meet the Paris Agreement goal to which countries agreed at a landmark United Nations climate conference in Nov 2015.
…Xu and Ramanathan point out that the goal is attainable. Global CO2 emissions had grown at a rate of 2.9 percent per year between 2000 and 2011, but had slowed to a near-zero growth rate by 2015. They credited drops in CO2 emissions from the United States and China as the primary drivers of the trend. Increases in production of renewable energy, especially wind and solar power, have also bent the curve of emissions trends downward. Other studies have estimated that there was by 2015 enough renewable energy capacity to meet nearly 24 percent of global electricity demand.
…most of the technologies needed to drastically curb emissions of short-lived climate pollutants already exist and are in use in much of the developed world. They range from cleaner diesel engines to methane-capture infrastructure.
“While these are encouraging signs, aggressive policies will still be required to achieve carbon neutrality and climate stability,” the authors wrote.
The historic Paris Agreement calls for limiting global temperature rise to “well below 2 °C.” Because of uncertainties in emission scenarios, climate, and carbon cycle feedback, we interpret the Paris Agreement in terms of three climate risk categories and bring in considerations of low-probability (5%) high-impact (LPHI) warming in addition to the central (∼50% probability) value. The current risk category of dangerous warming is extended to more categories, which are defined by us here as follows: >1.5 °C as dangerous; >3 °C as catastrophic; and >5 °C as unknown, implying beyond catastrophic, including existential threats. With unchecked emissions, the central warming can reach the dangerous level within three decades, with the LPHI warming becoming catastrophic by 2050. We outline a three-lever strategy to limit the central warming below the dangerous level and the LPHI below the catastrophic level, both in the near term (<2050) and in the long term (2100): the carbon neutral (CN) lever to achieve zero net emissions of CO2, the super pollutant (SP) lever to mitigate short-lived climate pollutants, and the carbon extraction and sequestration (CES) lever to thin the atmospheric CO2 blanket. Pulling on both CN and SP levers and bending the emissions curve by 2020 can keep the central warming below dangerous levels. To limit the LPHI warming below dangerous levels, the CES lever must be pulled as well to extract as much as 1 trillion tons of CO2 before 2100 to both limit the preindustrial to 2100 cumulative net CO2 emissions to 2.2 trillion tons and bend the warming curve to a cooling trend.
BY MARSHALL ABRAMCZYK, MARTHA CAMPBELL, AMAN CHITKARA, MIA DIAWARA, AILEEN LERCH, AND JAMES NEWCOMB
From the intro:
Today, many experts doubt that energy systems can decarbonize fast enough to prevent this scenario. But this belief is both dangerous and wrong—dangerous because despair undercuts the will to act; and wrong because this view does not take into account events already taking place that indicate a possible pathway to a rapid energy transition.
This paper describes scenarios for transitions in energy, agriculture, and land use that together are sufficient to limit global average temperature increase to 1.5–2 C°. Unlike conventional modeling approaches, these scenarios entail patterns of disruption, innovation, and nonlinear change, harnessed at global scale, that mirror the episodic and disruptive ways that individual industries and the economy as a whole have changed historically. The great transitions in the economy, such as the Industrial Revolution, have been driven by such self-reinforcing patterns of change. Their signs are all around us….
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.”
it was principally greenhouse gas emissions triggered by magma intrusions that caused the extinction through abrupt global warming and ocean acidification
The more science learns of these past greenhouse gas-driven events, the more uncomfortable the parallels to today become.
Geologically fast build-up of greenhouse gas linked to warming, rising sea-levels, widespread oxygen-starved ocean dead zones and ocean acidification are fairly consistent across the mass extinction events, and those same symptoms are happening today as a result of human-driven climate change.
….Of some 18 major and minor mass extinctions since the dawn of complex life, most happened at the same time as a rare, epic volcanic phenomenon called a Large Igneous Province (LIP). Many of those extinctions were also accompanied by abrupt climate warming, expansion of ocean dead zones and acidification, like today.
Earth’s most severe mass extinction, the “Great Dying,” began 251.94 million years ago at the end of the Permian period, with the loss of more than 90% of marine species…. why was the mass extinction event much shorter than the eruptions? And why did the extinction happen some 300,000 years after the lava began to flow?
….In other words, it wasn’t the lava, it was the underground magma that started the killing, by releasing greenhouse gases.
Norwegian scientist Henrik Svensen had earlier identified hundreds of unusual volcanic vents called “diatreme pipes” all over Siberia that connected underground intrusions of magma (“sills”) to the atmosphere, showing signs of violent gas explosions. This new work emphasizes the importance of Svensen’s 2009 conclusions:
The diatremes that have been mapped are the geologic representation of that gas escape on a catastrophic level. Our hypothesis is that the first sills to be intruded are the ones that really do the killing [by] large scale gas escape likely via these diatremes.
Svensen, who was not involved in Burgess’ study, commented:
The Burgess et al paper is a crucial step towards a new understanding of the role of volcanism in driving extinctions. It’s not the spectacular volcanic eruptions that we should pay attention too – it’s their quiet relative, the sub-volcanic network of intrusions, that did the job. The new study shows convincingly that we are on the right track.
Greenhouse gas as a killer
While other scientists have proposed that an array of killers may have been involved in the end-Permian mass extinction, from mercury poisoning to ultraviolet rays and ozone collapse to acid rain, Burgess argues that it was principally greenhouse gas emissions triggered by magma intrusions that caused the extinction through abrupt global warming and ocean acidification.
…Geologically fast build-up of greenhouse gas linked to warming, rising sea-levels, widespread oxygen-starved ocean dead zones and ocean acidification are fairly consistent across the mass extinction events, and those same symptoms are happening today as a result of human-driven climate change. Even though the duration of those past events was longer, and the volume of emissions was larger than we will produce, we are emitting greenhouse gases around 10 times faster than the most recent, mildest example – the PETM. The rapidity of today’s emissions prompted scientists Richard Zeebe and James Zachos to observe in a 2013 paper:
The Anthropocene will more likely resemble the end-Permian and end-Cretaceous disasters, rather than the PETM.
When the promises made for the 2016 Paris Agreement on climate change are added up, they aim to limit peak warming this century to about 3.3ºC compared to about 4.2ºC for the business-as-usual scenario, and the 2ºC limit the world is aiming to stay under. It’s sobering to compare those numbers to the majority of mass extinctions in the geological record which were characterized by abrupt warmings typically around 6-7ºC.
The temperature baseline used in the Paris climate agreement may have discounted an entire century’s worth of human-caused global warming, a new study has found.
Countries in the Paris climate agreement set a target of keeping warming below 2 degrees Celsius by curbing carbon emissions compared to their preindustrial levels. But a new study shows that the preindustrial level used in the agreement, based on temperature records from the late 19th century, doesn’t account for a potential century of rising temperatures caused by carbon dioxide emissions. Accounting for those gases, released from about 1750 to 1875, would add another one-fifth of a degree to the baseline temperature, the study found.
Published yesterday in Nature Climate Change, the research suggests there’s less time than previously believed to address global warming, said Michael Mann, a climatologist at Pennsylvania State University.
The study estimates that there may have already been 0.2 degree Celsius of warming, or 0.36 degree Fahrenheit, built into Earth, he said. That means the Paris Agreement would have to be more aggressive, according to the study, which was also written by researchers from the universities of Edinburgh and Reading in the United Kingdom.
“When you take that into account, it turns out we have 40 percent less carbon to burn than we thought we had,” Mann said….
Andrew P. Schurer, Michael E. Mann, et al. Importance of the pre-industrial baseline for likelihood of exceeding Paris goals Nature Climate Change doi:10.1038/nclimate5
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.
…The work shows that temperature rises measured over recent decades do not fully reflect the global warming already in the pipeline and that the ultimate heating of the planet could be even worse than feared.
….how much global temperatures rise for a certain level of carbon emissions is called climate sensitivity and is seen as the single most important measure of climate change. Computer models have long indicated a high level of sensitivity, up to 4.5C for a doubling of CO2 in the atmosphere.… the new work, using both models and paleoclimate data from warming periods in the Earth’s past, shows that the historical temperature measurements do not reveal the slow heating of the planet’s oceans that takes place for decades or centuries after CO2 has been added to the atmosphere.
…The new research, published in the journal Science Advances, has ended that. “The worrisome part is that all the models show there is an amplification of the amount of warming in the future,” he said. The situation might be even worse, as Proistosescu’s work shows climate sensitivity could be as high as 6C.
….“The models simulate a warming pattern like today’s, but indicate that strong feedbacks kick in when the Southern Ocean and Eastern Equatorial Pacific eventually warm, leading to higher overall temperatures than would simply be extrapolated from the warming seen to date,” said [co-author] Peter Huybers…“But there is no perfect analogue for the changes that are coming.”
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