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Tag Archive: emissions

  1. Microwave appliance usage could be as bad for the environment as cars, suggests new research

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    • Microwave appliance usage emits 7.7 million tonnes of carbon dioxide equivalent per year in the EU. This is equivalent to the annual emissions of 6.8 million cars.
    • Microwave appliance usage across the EU consumes an estimated 9.4 terawatts per hour (TWh) of electricity every year. This is equivalent to the annual electricity generated by three large gas power plants.

    January 17, 2018  University of Manchester read full ScienceDaily article here

    Microwave appliance usage across the EU alone emits as much carbon dioxide as nearly seven million cars, according to a new study by The University of Manchester.

    Researchers at the University have carried out the first ever comprehensive study of the environmental impacts of microwave appliances, considering their whole life cycle, from ‘cradle to grave’.

    The study found:

    • Microwave appliance usage emits 7.7 million tonnes of carbon dioxide equivalent per year in the EU. This is equivalent to the annual emissions of 6.8 million cars.
    • Microwave appliance usage across the EU consumes an estimated 9.4 terawatts per hour (TWh) of electricity every year. This is equivalent to the annual electricity generated by three large gas power plants.
    • Efforts to reduce consumption should focus on improving consumer awareness and behaviour to use appliances more efficiently…

    Alejandro Gallego-Schmid, Joan Manuel F. Mendoza, Adisa Azapagic. Environmental assessment of microwaves and the effect of European energy efficiency and waste management legislation. Science of The Total Environment, 2018; 618: 487 DOI: 10.1016/j.scitotenv.2017.11.064

  2. Uncertainty surrounds US livestock methane emission estimates

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    • Per the EPA the top three sources of anthropogenic methane in the US are the combined energy sector—natural gas, petroleum systems and coal mining 40%; livestock, 36%; and landfills, 18%.
    • research around the world has shown that variability in enteric methane emissions largely can be explained with variability in feed dry-matter intake

    November 30, 2017, Pennsylvania State University  read full phys.org article here

    A new study of methane emissions from livestock in the United States ….has challenged previous top-down estimates.

    The research was conducted because serious discrepancies exist between top-down estimates that suggest the U.S. Environmental Protection Agency is underestimating agricultural emissions by up to 90 percent, and bottom-up estimates accepted by the federal government showing lower emissions.

    Top-down emissions estimates involve monitoring atmospheric methane concentrations by satellites or from air samples collected at high altitude by planes, and using models to estimate the sources of emissions. Bottom-up estimates take into account populations and animal emission factors.

    In their detailed analysis, researchers used a spatially explicit, bottom-up approach, based on animal inventories and feed-intake-based emission factors, to estimate enteric methane emissions for and methane emissions for cattle, swine and poultry for the contiguous United States.

    The researchers estimated methane emissions using a “gridded” approach, dividing the U.S. into 0.1 by 0.1-degree GIS units, which created cells from 31 square miles in the northern United States to 42 square miles in the southern part of the country.

    ….According to the EPA, the top three sources of anthropogenic methane in the United States are the combined energy sector—natural gas, petroleum systems and coal mining—which makes up 40 percent of the total; livestock, 36 percent of the total; and landfills, 18 percent of the total.

    …Methane emissions from livestock operations are the result of microbial fermentation and methanogenesis in the forestomach of ruminants and similar fermentation processes in manure from both ruminant and non-ruminant farm .

    Methane is also produced from enteric fermentation in the digestive tract of non-ruminant herbivore species, such as horses, donkeys and mules, as a result of fermentation processes in their hindgut. However, “hindgut fermenters” do not produce nearly as much methane per unit of fermented feed as ruminants, so enteric or manure emissions from equine species were not included in this analysis. Neither were emissions from small ruminants such as sheep and goats, which are negligible in the U.S.

    …Overall, the research, which was published this month in Environmental Science and Technology, yielded total U.S. livestock methane emissions of 19.6 billion pounds per year. However, uncertainty surrounding that total is high, researchers acknowledged.

    …predicting methane emissions from manure is a more complex process and carries a larger uncertainty in the estimates, the researchers pointed out. Manure composition, type of storage facilities and manure retention time, and environment—particularly temperature—are among the factors that affect methane emissions from manure.

    There is great uncertainty in both enteric and manure methane emissions from livestock, Hristov conceded. He said that research around the world has shown that variability in enteric methane emissions largely can be explained with variability in feed dry-matter intake. Nutrient composition of the feed is also important but has a lesser impact on enteric methane production.

    Uncertainty surrounds US livestock methane emission estimates The researchers estimated methane emissions using a “gridded” approach, dividing the US into 0.1- by 0.1-degree GIS units, which created cells from 31 square miles in the northern United States to 42 square miles in the southern part of the country. The study pegged total U.S. livestock methane emissions of 19.6 billion pounds per year. This map shows where they are coming from. Credit: Penn State

    Read more at: https://phys.org/news/2017-11-methane-emissions-livestock.html#jCp

  3. Transformation to wind and solar achievable with lower full life cycle GHG emissions compared to other energy technologies

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    • Electricity production from biomass, coal, gas and hydropower for instance induces much higher indirect greenhouse gas emissions than nuclear electricity, or wind and solar-based power supply
    • Scaling up wind and solar technologies would induce only modest indirect GHG emissions compared to other energy power technologies
    December 8, 2017 Potsdam Institute for Climate Impact Research (PIK)  read full ScienceDaily article here
    Different low carbon technologies from wind or solar energy to fossil carbon capture and sequestration (CCS) differ greatly when it comes to indirect GHG emissions in their life cycle. The new study finds that wind and solar energy belong to the more favorable when it comes to life-cycle emissions and scaling up these technologies would induce only modest indirect GHG emissions — and hence not impede the transformation towards a climate-friendly power system….

    “Both fossil and non-fossil power technologies still come with a certain amount of greenhouse gas emissions within their life cycle — on the one hand because it needs energy to construct and operate them, on the other hand because of methane emissions, e.g. from coal and gas production,” explains lead author Michaja Pehl. “However, we found there are substantial differences across technologies regarding their greenhouse gas balance. Electricity production from biomass, coal, gas and hydropower for instance induces much higher indirect greenhouse gas emissions than nuclear electricity, or wind and solar-based power supply.”….

    ….”When it comes to life cycle greenhouse gas emissions, wind and solar energy provide a much better greenhouse gas balance than fossil-based low carbon technologies, because they do not require additional energy for the production and transport of fuels, and the technologies themselves can be produced to a large extend with decarbonized electricity,” states Edgar Hertwich, an industrial ecologist from Yale University who co-authored the study. Due to technological innovation, less and less energy will be needed to produce wind turbines and solar photovoltaic systems….

    Michaja Pehl, Anders Arvesen, Florian Humpenöder, Alexander Popp, Edgar G. Hertwich, Gunnar Luderer. Understanding future emissions from low-carbon power systems by integration of life-cycle assessment and integrated energy modelling. Nature Energy, 2017; 2 (12): 939 DOI: 10.1038/s41560-017-0032-9

  4. Cities can cut greenhouse gas emissions far beyond their urban borders

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    • Upstream emissions may occur anywhere in the world and are roughly equal in size to the total emissions originating from a city’s own territory, a new study shows.
    • Cities should be encouraged and enabled to focus on their full emission spectrum — local and upstream — as they continue to develop their climate mitigation plans.
    • Among the cities studied, Berlin’s global hinterland is largest, with more than half of its upstream emissions occurring outside of Germany, mostly in Russia, China and across the European Union.
    • 20% of Mexico City’s considerably smaller upstream emissions occur outside Mexico, mainly in the US and China.

    November 7, 2017 Potsdam Institute for Climate Impact Research (PIK)

    Greenhouse gas emissions caused by urban households’ purchases of goods and services from beyond city limits are much bigger than previously thought. These upstream emissions may occur anywhere in the world and are roughly equal in size to the total emissions originating from a city’s own territory, a new study shows. This is not bad news but in fact offers local policy-makers more leverage to tackle climate change, the authors argue in view of the UN climate summit COP23 that just started…
    The planned emission reductions presented so far by national governments at the UN summit are clearly insufficient to limit global warming to well below 2 degrees Celsius, the target agreed by 190 countries, therefore additional efforts are needed.

    If a city instead chooses to foster low carbon construction materials this can drastically reduce its indirect CO2 emissions. Even things that cities are already doing can affect far-away emissions. Raising insulation standards for buildings for example certainly slashes local emissions by reducing heating fuel demand. Yet it can also turn down the need for electric cooling in summer which reduces power generation and hence greenhouse gas emissions in some power plant beyond city borders.

    By choosing energy from solar or wind, city governments could in fact close down far-away coal-fired power plants….

    Peter-Paul Pichler, Timm Zwickel, Abel Chavez, Tino Kretschmer, Jessica Seddon, Helga Weisz. Reducing Urban Greenhouse Gas Footprints. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-15303-x

  5. Bad news: Global emissions rising again

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    • In 2017, CO2 emissions from fossil fuels and industry are projected to grow by 2% (0.8% to 3%). This follows three years of nearly no growth (2014-2016). (GDP to rise 3.6% according to IMF figures).
    • Global CO2 emissions from all human activities are set to reach 41 billion tonnes (41 Gt CO2) by the end of 2017. Meanwhile emissions from fossil fuels are set to reach 37 Gt CO2 — a record high.
    • Atmospheric CO2 concentration reached 403 parts per million in 2016, and is expected to increase by 2.5 ppm in 2017.
    • [and some good news] CO2 emissions decreased in the presence of growing economic activity in 22 countries representing 20 per cent of global emissions; Renewable energy has increased rapidly at 14% per year over the last five years — albeit from a very low base.

    November 13, 2017 University of East Anglia read full ScienceDaily article here

    Global carbon emissions are on the rise again in 2017 after three years of little to no growth. Global emissions from all human activities will reach 41 billion tons in 2017, following a projected 2 percent rise in burning fossil fuels. It was hoped that emissions might soon reach their peak after three stable years, so this is an unwelcome message for policy makers and delegates at the UN Climate Change Conference (COP 23) in Bonn this week.

    The research, published today simultaneously in the journals Nature Climate Change, Earth System Science Data Discussions and Environmental Research Letters, reveals that global emissions from all human activities will reach 41 billion tonnes in 2017, following a projected 2% rise in burning fossil fuels.

    The figures point to China as the main cause of the renewed growth in fossil emissions — with a projected growth of 3.5%.

    CO2 emissions are expected to decline by 0.4% in the US and 0.2% in the EU, smaller declines than during the previous decade.

    Increases in coal use in China and the US are expected this year, reversing their decreases since 2013….

    ….[some good news] CO2 emissions decreased in the presence of growing economic activity in 22 countries representing 20 per cent of global emissions….

    Glen P. Peters et al. Towards real-time verification of CO2 emissions. Nature Climate Change, 2017; DOI: 10.1038/s41558-017-0013-9

  6. Urgent emission reductions needed to achieve 1.5°C warming limit; “not yet geophysically impossible” but requires ambitious emissions reductions

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    • limiting the increase in global average temperatures above pre-industrial levels to 1.5°C is not yet geophysically impossible, but likely requires more ambitious emission reductions than those pledged so far
    • Contrary to many other studies, this finds we have more than 700 billion tons left to emit to keep warming within 1.5 degrees Celsius, with a two-thirds probability of success. “That’s about 20 years at present-day emissions
    • From their study: Emission budgets and pathways consistent with limiting warming to 1.5°C [abstract below]
      • Assuming emissions peak and decline to below current levels by 2030, and continue thereafter on a much steeper decline, which would be historically unprecedented but consistent with a standard ambitious mitigation scenario (RCP2.6), results in a likely range of peak warming of 1.2–2.0°C above the mid-nineteenth century.
      • limiting warming to 1.5°C is not yet a geophysical impossibility, but is likely to require delivery on strengthened pledges for 2030 followed by challengingly deep and rapid mitigation
    September 18, 2017 University of Oxford read full ScienceDaily article here

    [Scientists] investigated the geophysical likelihood of limiting global warming to “well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C.”  …the paper concludes that limiting the increase in global average temperatures above pre-industrial levels to 1.5°C, the goal of the Paris Agreement on Climate Change, is not yet geophysically impossible, but likely requires more ambitious emission reductions than those pledged so far….

    ….’This paper shows that the Paris goals are within reach, but clarifies what the commitment to ‘pursue efforts to limit the temperature increase to 1.5°C’ really implies. Starting with the global review due next year, countries have to get out of coal and strengthen their existing targets so as to keep open the window to the Paris goals. The sooner global emissions start to fall, the lower the risk not only of major climatic disruption, but also of the economic disruption that could otherwise arise from the need for subsequent reductions at historically unprecedented rates, should near-term action remain inadequate.’…

    A group of prominent scientists on Monday created a potential whiplash moment for climate policy, suggesting that humanity could have considerably more time than previously thought to avoid a “dangerous” level of global warming. The upward revision to the planet’s influential “carbon budget” was published by a number of researchers who have been deeply involved in studying the concept, making it all the more unexpected. But other outside researchers raised questions about the work, leaving it unclear whether the new analysis — which, if correct, would have very large implications — will stick.In a study published in the journal Nature Geoscience, a team of 10 researchers, led by Richard Millar of the University of Oxford, recalculated the carbon budget for limiting the Earth’s warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit) above temperatures seen in the late 19th century. It had been widely assumed that this stringent target would prove unachievable — but the new study would appear to give us much more time to get our act together if we want to stay below it.

    What this paper means is that keeping warming to 1.5 degrees C still remains a geophysical possibility, contrary to quite widespread belief,” Millar said in a news briefing…..

    It is very hard to see how we could still have a substantial CO2 emissions budget left for 1.5 °C, given we’re already at 1 °C, thermal inertia means we’ll catch up with some more warming even without increased radiative forcing, and any CO2 emissions reductions inevitably comes with reduced aerosol load as well, the latter reduction causing some further warming,” Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research in Germany said by email.

    …In 2013, the United Nations’ Intergovernmental Panel on Climate Change (IPCC) calculated that humanity could emit about 1,000 more gigatons, or billion tons, of carbon dioxide from 2011 onward if it wanted a good chance of limiting warming to 2 degrees C — launching the highly influential concept of the “carbon budget.”

    The allowable emissions or budget for 1.5 degrees C would, naturally, be lower. One 2015 study found they were 200 billion to 400 billion tons. And we currently emit about 41 billion tons per year, so every three years, more than 100 billion tons are gone. No wonder a recent study put the chance of limiting warming to 1.5 degrees C at 1 percent. Peters said that according to the prior paradigm, we basically would have used up the carbon budget for 1.5 degrees Celsius by the year 2022.

    That’s what makes the new result so surprising: It finds that we have more than 700 billion tons left to emit to keep warming within 1.5 degrees Celsius, with a two-thirds probability of success. “That’s about 20 years at present-day emissions,” Millar said at the news briefing….

    Richard J. Millar, Jan S. Fuglestvedt, Pierre Friedlingstein, Joeri Rogelj, Michael J. Grubb, H. Damon Matthews, Ragnhild B. Skeie, Piers M. Forster, David J. Frame & Myles R. Allen. Emission budgets and pathways consistent with limiting warming to 1.5°C. Nature Geoscience Published online doi:10.1038/ngeo3031

    ABSTRACT: The Paris Agreement has opened debate on whether limiting warming to 1.5°C is compatible with current emission pledges and warming of about 0.9°C from the mid-nineteenth century to the present decade. We show that limiting cumulative post-2015 CO2 emissions to about 200GtC would limit post-2015 warming to less than 0.6°C in 66% of Earth system model members of the CMIP5 ensemble with no mitigation of other climate drivers, increasing to 240GtC with ambitious non-CO2 mitigation. We combine a simple climate–carbon-cycle model with estimated ranges for key climate system properties from the IPCC Fifth Assessment Report. Assuming emissions peak and decline to below current levels by 2030, and continue thereafter on a much steeper decline, which would be historically unprecedented but consistent with a standard ambitious mitigation scenario (RCP2.6), results in a likely range of peak warming of 1.2–2.0°C above the mid-nineteenth century. If CO2 emissions are continuously adjusted over time to limit 2100 warming to 1.5°C, with ambitious non-CO2 mitigation, net future cumulative CO2 emissions are unlikely to prove less than 250GtC and unlikely greater than 540GtC. Hence, limiting warming to 1.5°C is not yet a geophysical impossibility, but is likely to require delivery on strengthened pledges for 2030 followed by challengingly deep and rapid mitigation. Strengthening near-term emissions reductions would hedge against a high climate response or subsequent reduction rates proving economically, technically or politically unfeasible.

  7. The Great Decoupling: the story of energy use, economic growth, and carbon emissions in four charts.

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    July 2017 see article and visualizations at AnthropoceneMagazine here

    …For the past 15 years, global economic growth rose twice as fast as global energy demand and CO2 emissions. The changes have been the most dramatic since 2010. And within the past three years (2014–2016), emissions stabilized—at least temporarily—while the global economy continued growing. That is a first.

    ….Energy efficiency is responsible for most of the decoupling to date. But the transformation to zero carbon fuels must dramatically accelerate to keep up with growing energy demands and increasing world population. Only then will decoupling be complete….

  8. Allowing polluters to offset carbon emissions by paying forest owners effectively reduces greenhouse gases, Stanford study finds

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    • A pioneering California program to sell carbon offsets has surprising environmental benefits – including providing habitat for endangered species – and provides lessons for initiatives under development in other states and countries.
    • The program as a whole leads to emissions reductions that wouldn’t have occurred otherwise, the Stanford scientists found after analyzing metrics used to confirm individual projects’ robustness.

    See more here: Carbon Offsets Really Do Help Lower Emissions Aug 15 2017 Scientific American

    By Rob Jordan August 14, 2017 read full Stanford News article here

    You can’t grow money on trees, but you can earn money for letting trees grow. Or at least you can through a pioneering California program that allows forest owners around the United States to sell carbon credits to companies required by the state to reduce emissions. Researchers at Stanford analyzed the program and found that the initiative has valuable environmental benefits beyond just offsetting greenhouse gases….

    ….“California provides the first proof of concept with a government program that credits standing forests.”

    ….Forest offsets, which account for the majority of offsets in California’s cap and trade market, involve forest owners changing the way they manage their land so trees will store more carbon…cutting trees less often, reforesting previously forested land or improving forests through various management practices…

    For each additional ton of carbon dioxide their trees store, forest owners can earn a credit – worth about $10 currently – to sell to California companies required to reduce or offset their greenhouse gas emissions. Since it started in 2013, the program has earned forest owners about $250 million, while offsetting 25 million tons of carbon – an amount equal to 5 percent of California’s annual passenger vehicle emissions.

    …Although California’s cap and trade program allows the use of forest offsets up to an amount equaling 8 percent of a polluter’s emissions, the volume issued so far is only 2 percent of total capped emissions. Because the pool of available offsets is quite small, polluters still need to reduce their own emissions directly, rather than relying on purchasing offsets. The program as a whole leads to emissions reductions that wouldn’t have occurred otherwise, the Stanford scientists found after analyzing metrics used to confirm individual projects’ robustness.

    Still, Anderson and her co-authors warn against using forest offsets in large numbers because they may distract from urgent and drastic emissions reduction priorities elsewhere….

    Anderson, Christa M, Field, Christopher B, Mach, Katharine J. Forest offsets partner climate-change mitigation with conservation. Front Ecol Environ 2017; 15(7): 359365, doi:10.1002/fee.1515

  9. 10 Cities Taking a Nature-Driven Approach to Innovation

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    • Our most advanced and sophisticated cities also need to be sustainable and preserve natural areas
    • The smartest cities in the world are integrating nature to create a truly sustainable city.
    BY SKIP DESCANT / AUGUST 4, 2017 read full govtech article here

    It’s not enough for the country’s most advanced and sophisticated cities to be at the forefront of technological innovation with “smart” parking meters or informational kiosks. They also need to be sustainable and show an ability to preserve natural areas, according to Anil Ahuja, an engineering professional regarded as the “Smart Cities Guru” and author of the 2016 book Integration of Nature and Technology for Smart Cities.

    Ahuja has compiled the Top Ten U.S. Cities Integrating Nature & Technology report to highlight which cities are leaders at balancing new technology with good nature policies.

    “A smart city doesn’t just provide technology or economic solutions,” he said in a statement. “The smartest cities in the world are integrating nature to create a truly sustainable city. I have identified a number of cities in the United States that are excellent examples for other smart cities to model themselves after.”

    …[For example] Portland, Ore., promotes energy efficiency through a number of residential, commercial and government initiatives. It was the first city to create a local action plan to reduce carbon emissions. Portland aims to reduce emissions by 40 percent by 2030 and 80 percent by 2050.

    Ahuja’s top cities for integrating nature and technology listed alphabetically are:

    • Boston – Engaging its citizens through crowdsourced mobile technology to enable smart government.
    • Chicago – Leveraging data to make cities healthier, more efficient and more livable.
    • Los Angeles – Leveraging big data, mobile and cloud based technologies to save energy and improve efficiency.
    • New York – Maximizing real-time traffic information to reduce congestion, improve the flow of traffic and decrease carbon emissions.
    • Orlando – Recognized for its approach to smart operation of transportation, security and emergency management and energy waste reduction programs.
    • Portland, Ore. – Investing in IoT sensor networks and leveraging smart agriculture applications and big data to benefit the local region.
    • San Diego – Adopting the Climate Action Plan, which will improve public health and air quality, conserve water, and use current resources more efficiently.
    • San Francisco – Multiple initiatives including waste reduction, electric car charging and building performance optimization.
    • Seattle – A pioneer and leader for establishing and increasing the adoption of green standards.
    • Washington, D.C. – A leader in smart mobility and for its ratio of park acres to citizens.
  10. How California Plans to Go Far Beyond Any Other State on Climate

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      Read full NY Times article here

    Last August, the State Legislature set a goal of slashing emissions more than 40 percent below today’s levels by 2030, a far deeper cut than President Barack Obama proposed for the entire United States and deeper than most other countries have contemplated. So how will California pull this off?

    On Tuesday, Gov. Jerry Brown signed a new law expanding the state’s cap-and-trade program, which is expected to play a big role. But cutting greenhouse gases this deeply will involve more than cap and trade. The state plans to rethink every corner of its economy, from urban planning to dairy farms.

    Until now, most states have followed a standard playbook for curbing emissions. Market forces have replaced older coal plants with cheaper and cleaner natural gas, while state mandates have added modest shares of wind and solar power to the grid. As a result, domestic carbon dioxide emissions have fallen 14 percent since 2005 at relatively little cost.

    But California has now plucked most of that low-hanging fruit. The state’s emissions are nearly back to 1990 levels, it barely uses any coal and it has installed as many solar panels as the rest of the country combined. Per capita, California has the third-lowest emissions in the nation, after New York and the District of Columbia, which means further cuts will come less easily than they would for a state like Texas.

    “Each additional increment of carbon reduction is tougher than the previous one,” said Dan Reicher, director of the Center for Energy Policy and Finance at Stanford. He added, “California will have to reach deeper into the bag of technologies” to cut emissions from more stubborn polluters like oil refineries and cement plants.

    …In January, California’s Air Resources Board, which has broad latitude to carry out the state’s climate laws, detailed one possible strategy for cutting emissions 40 percent below 1990 levels by 2030.

    First, by law, California must get 50 percent of its electricity from renewable sources by 2030, up from 25 percent today. That’s a herculean task in itself: The state is already straining to cope with sharp swings in solar power during afternoons and will soon have to juggle ever-larger shares of intermittent renewable electricity, by deploying batteries, reworking its grid or taking other novel approaches.

    Second, the board envisioned the number of electric cars and other zero-emissions vehicles on California’s roads rising to 4.2 million by 2030 from 250,000 today. Freight trucks would have to become more efficient or electrified, while cities would need to adopt far-reaching strategies to promote mass transit, biking and walking.

    But a major push on renewable power and transportation would get California just one-fourth of the way toward its goal. Other cuts would come from doubling efficiency savings from buildings and industry, no mean feat in a state that already has some of the strictest building codes in the country. The state would also need to lower the carbon content of its gasoline supply under the Low Carbon Fuel Standard, possibly by increasing biofuel use.

    One-third of the reductions in the proposal would come from curbing emissions of methane — a potent greenhouse gas — from landfills, wastewater facilities and manure piles at dairy farms. No state has ever regulated agriculture so aggressively, and dairy farmers are pushing back, warning that capturing methane from millions of cows could prove untenable.

    …So, as a complement to these efforts, Mr. Brown insisted on expanding another major program: cap and trade.Mr. Brown has promoted California’s policies as a way of convincing the world that the United States won’t abandon the fight against climate change, even after Mr. Trump announced a withdrawal from the Paris climate agreement. “I want to do everything we can to keep America on track, keep the world on track,” Mr. Brown said in May.

    California is responsible for only 1 percent of global emissions. But it could contribute even more to the world’s efforts by advancing new tools to tackle climate change, like floating deepwater wind farms.

    If the state stumbles, that could provide valuable lessons, too. By 2030, California plans to close its last nuclear power plant, Diablo Canyon, which provides 9 percent of the state’s electricity. The idea is to replace that lost power with renewables and efficiency. If that proves unworkable, it could offer a warning to other states facing nuclear shutdowns.

    California’s push to make cap and trade effective could also have global ramifications, especially since Europe has failed to gain traction with its emissions-trading program and China is testing its own version