底特律-总统乔·拜登为了实现他雄心勃勃的目标，即到2030年将美国的温室气体排放量削减一半，大规模的减排将不得不来自除了汽车尾气这一罪魁祸首之外的某个地方。

专家说，这是因为在不到十年的时间里，美国有太多的燃气乘用车——约2.79亿辆——无法替代它们。在一个典型的年份里，汽车制造商在全国销售约1700万辆汽车。即使每一个新的都是电动的，也需要16年以上的时间来更换整个车队。

此外，汽车在报废前平均在美国道路上停留近12年，这意味着天然气燃料汽车将在未来许多年占据主导地位。

波士顿咨询集团(Boston Consulting Group)董事总经理、一份关于电动汽车采用情况的研究报告的作者Aakash Arora表示:“仅靠新车销售，我们无法实现目标。”“舰队太大了。”

因此，除非政府的激励措施能够以某种方式说服大多数美国人放弃汽车和卡车，购买电动汽车，否则将尾气排放减少近50%的时间将远远超过拜登的时间表。去年，在美国销售的新车中，全电动汽车不到2%。

俄亥俄州立大学机械工程教授兼智能移动主管克里斯·阿特金森(Chris Atkinson)表示:“如果今天销售的每辆新车都是电动汽车，并且一夜之间完全由可再生能源驱动，我们将需要10年或更长时间才能实现温室气体排放减少50%。”

这意味着其他经济部门将不得不大幅削减温室气体排放，以弥补汽车行业的不足。

交通运输作为一个整体，不仅包括汽车和卡车，还包括船只和飞机，是这种污染的最大来源。在2019年美国排放的近660万公吨二氧化碳中，交通运输产生了29%。接下来是25%的发电量。然后是工厂，占23%，商业和住宅建筑占13%，农业占10%。

发电是最有可能更快减排的来源。该行业已经取得了重大进展。根据政府的劳伦斯·伯克利国家实验室的数据，去年发电的碳排放量比政府预计的2005年要低52%。原因是:更多地使用天然气、太阳能和风能，以及随着经济的发展实现能源效率的提高，需求减少。

拜登周四在与世界领导人的气候峰会上公布了他的目标，但他尚未详细说明他的政府设想的每个经济部门的温室气体减排。总的来说，这些削减旨在限制全球变暖，这是总统愿景的一部分，即建立一个生产尖端电池和电动汽车的国家，一个更高效的电网，并覆盖废弃的石油钻井平台和煤矿。

拜登的最高气候顾问吉娜·麦卡锡(Gina McCarthy)周四似乎发出信号，要实现这些目标，必须从汽车行业以外的其他行业进一步削减排放量。她为政府的决定进行了辩护，该决定没有为停止销售新的燃气汽车或实现交通部门的净零排放设定具体的最后期限。

麦卡锡说，在没有交通目标的情况下，“我们有很多方法”将美国的温室气体排放量减半。

对于交通部门，政府表示将提高车辆效率，投资低碳可再生燃料，并对交通、铁路和自行车进行改进。政府还希望将拥有65万辆汽车的联邦车队转换为电池供电。

为了增加电动汽车的销量，政府计划在2030年前花费150亿美元建造50万个充电站，并提供未具体说明的税收抵免和退税来降低成本。

将整个燃气燃烧器车队换成电动汽车可能需要20年以上的时间。IHS Markit汽车副总监托德·坎普(Todd Campau)估计，到2025年，美国道路上主要以天然气为动力的车辆数量将继续增长，达到2.84亿辆。

“就需要交换的数量而言，情况只会越来越糟，”坎普说。

他和其他人说，需要非常有吸引力的政府激励措施来吸引更多的人离开他们的煤气灶——类似于2009年纽约参议院多数党领袖查克·舒默提出的旧车换现金计划，但规模要大得多。舒默的计划提议给予人们至少3000美元的回扣，以淘汰燃烧汽车，生产电动汽车。

总部位于柏林的气候智库气候分析(Climate Analytics)的主任比尔·黑尔(Bill Hare)预测，随着电动汽车数量的增长，2030年后运输行业的污染将会减少。

“到那时，你最终会看到运输行业或多或少的完全脱碳——但要到2050年，”他说。

研究公司铑集团(Rhodium Group)的董事凯特·拉森(Kate Larsen)表示，即使排气尾管排放量不能迅速减少，拜登的目标也可以通过大幅削减电厂排放量、减少油井甲烷污染以及削减制冷和空调中使用的氢氟碳化合物来实现。拉森说，研究表明，通过投资和监管的结合，到2030年电力排放可以减少80%。

“这将让我们走完大部分路程，”她说。“我们不会看到50%的全面削减。”

她说，零排放发电为将汽车和许多其他污染源转化为电力奠定了基础。

波士顿咨询公司(Boston Consulting)的一份报告显示，即使是在电动汽车采用方面领先于美国的国家，主要是欧洲和中国，估计销量仍不会达到2030年二氧化碳减排目标。在欧洲，有着强大的激励机制和严格的污染限制，纯电池和插电式混合动力车的市场份额去年从3%跃升至10.5%。这远远不够。

“如果2035年全球销售的新车有一半是零排放汽车，那么70%的道路车辆仍将使用汽油或柴油，”报告称。

由于缺乏制造电池的工厂产能，更快的采用也可能受到限制。例如，美国只有四家工厂在建或在建。OSU的阿特金森说，整个舰队需要50节电。

即便如此，从内燃机到电动汽车的转变正在进行中，波士顿咨询公司表示，这一转变将会加速。该公司预计，新的插电式混合动力和电池电动汽车的销量将从2020年占全球市场的12%上升到2025年的47%。报告指出，电池成本正在下降，汽车制造商计划到2023年推出300款新的电动汽车，给消费者提供大量选择。

波士顿咨询公司报告的作者内森·尼斯说:“有一条路可以走得很快。”。“商业正朝着这个方向发展。政府可以成为最重要的加速器。”

America's gas-fueled vehicles imperil Biden's climate goals

DETROIT -- For PresidentJoe Bidento reach his ambitious goal of slashing America’s greenhouse gas emissions in half by 2030, huge reductions would have to come from somewhere other than one of the worst culprits: auto tailpipes.

That’s because there are just too many gas-powered passenger vehicles in the United States — roughly 279 million — to replace them in less than a decade, experts say. In a typical year, automakers sell about 17 million vehicles nationwide. Even if every one of the new ones were electric, it would take more than 16 years to replace the whole fleet.

What's more, vehicles now remain on America's roads for an average of nearly 12 years before they're scrapped, which means that gas-fueled vehicles will predominate for many years to come.

“We're not going to be able to meet the target with new-car sales only," said Aakash Arora, a managing director with Boston Consulting Group and an author of a study on electric vehicle adoption. “The fleet is too big.”

So unless government incentives could somehow persuade a majority of Americans to scrap their cars and trucks and buy electric vehicles, reducing tailpipe emissions by anything close to 50% would take far longer than the Biden timetable. Last year, fewer than 2% of new vehicles sold in the United States were fully electric.

“If every new vehicle sold today was an electric vehicle and it was entirely powered by renewable energy overnight, it would take 10 years or more for us to achieve a 50% reduction in greenhouse gas emissions,” said Chris Atkinson, a professor of mechanical engineering and director of smart mobility at Ohio State University.

Which means that other sectors of the economy would have to slash greenhouse gas emissions deeply enough to make up the shortfall in the auto industry.

Transportation as a whole, which includes not only cars and trucks but also ships and airplanes, is the single largest source of such pollution. Of the nearly 6.6 million metric tons of carbon dioxide that were emitted in the United States in 2019, transportation produced 29%. Next was electricity generation at 25%. Then came factories at 23%, commercial and residential buildings at 13% and agriculture at 10%.

Electricity generation is the most likely source of faster reductions. That sector has already made major strides. Last year, carbon emissions from electricity generation were 52% lower than the government had projected they would be in 2005, according to government’s Lawrence Berkeley National Laboratory. The reasons: more use of natural gas, solar and wind power, as well as reduced demand as the economy has evolved to achieve gains in energy efficiency.

Biden, who unveiled his goals at a climate summit with world leaders Thursday, has yet to detail the greenhouse gas reductions that his administration envisions for each sector of the economy. Overall, the reductions are intended to limit global warming as part of the president's vision of a nation that produces cutting-edge batteries and electric cars, a more efficient electrical grid and caps abandoned oil rigs and coal mines.

Gina McCarthy, Biden’s top climate adviser, appeared to signal Thursday that deeper cuts in emissions would have to come from sectors other than the auto industry to reach the goals. She defended the administration’s decision not to set a specific deadline for ending sales of new gas-powered cars or for achieving net-zero emissions from the transportation sector.

“We have a whole lot of ways” to cut U.S. greenhouse gas emissions in half without a transportation goal, McCarthy said.

For the transportation sector, the government says it will improve vehicle efficiency, invest in low-carbon renewable fuels and produce transit, rail and bicycling improvements. The administration also wants to convert the 650,000-vehicle federal vehicle fleet to battery power.

To increase sales of electric vehicles, the administration plans to spend $15 billion to build a half-million charging stations by 2030, as well as offer unspecified tax credits and rebates to cut the cost.

Swapping the entire fleet of gas burners for electric vehicles could take even longer than 20 years. Todd Campau, associate director of automotive for IHS Markit, estimates that the number of mostly gas-powered vehicles on U.S. roads, will keep growing — to 284 million by 2025.

“The situation is only getting worse as far as the volume that needs to be exchanged,” Campau said.

He and others say it would take highly attractive government incentives to lure additional people out of their gas-burners — something like a reprise of the 2009 cash-for-clunkers program proposed by Senate Majority Leader Chuck Schumer of New York, but on a vastly larger scale. The Schumer plan proposes rebates of at least $3,000 for people to scrap combustion vehicles for electrics.

Bill Hare, director of Climate Analytics, a Berlin-based climate think tank, predicted that pollution reductions in the transportation sector will come after 2030 as the electric vehicle fleet grows.

“What you would then end up seeing is more or less complete decarbonization of the transport sector — but by 2050,” he said.

Even if tailpipe emissions can't be cut quickly, Biden's goals can be reached with significant cuts in electric powerplant emissions as well as reductions in methane pollution from oil wells and cuts in hydrofluorocarbons used in refrigeration and air conditioning, said Kate Larsen, director at Rhodium Group, a research firm. Studies show that electric power emissions can be cut 80% by 2030 with a mix of investment and regulations, Larsen said.

“That will get us the bulk of the way,” she said. “We won't see 50% reductions across the board.”

Zero emissions electric generation sets the stage for converting cars and many other pollution sources to electricity, she said.

Even countries that are ahead of the U.S. in electric vehicle adoption, mainly in Europe and China, estimates are that sales still won't put enough electric vehicles in use to reach 2030 carbon dioxide reduction goals, according to a Boston Consulting report. In Europe, which has strong incentives and strict pollution limits, the market share of battery-only and plug-in hybrids jumped from 3% to 10.5% last year. That's far from enough.

"If half of new cars sold around the world in 2035 are zero-emission vehicles, 70% of the vehicles on roads will still be burning gasoline or diesel," the report said.

Faster adoption could be limited, too, by a lack of factory capacity to make batteries. The U.S., for instance, has only four plants that are either built or in the works. It would need 50 to electrify the entire fleet, said OSU’s Atkinson.

Even so, a switch from internal combustion to electric vehicles is well under way, and Boston Consulting says it will accelerate. The company foresees new plug-in hybrid and battery electric vehicle sales rising from 12% of the global market in 2020 to 47% in 2025. It notes that battery costs are falling and automakers plan to introduce 300 new EV models by 2023, giving consumers a huge array of choices.

“There's a path for this to move quite quickly,” said Nathan Niese, an author of the Boston Consulting report. “Business is moving in that direction. The government can just be the accelerator on top of that.”