Every region of the US is already feeling the effects of climate change but policymakers are still not doing enough to reduce greenhouse gas (GHG) emissions, according to a new report from US government scientists.
The fifth National Climate Assessment, a congressionally mandated report released around every five years, is the product of 14 federal agencies and hundreds of authors. It offers largely similar conclusions as prior iterations, namely that fossil fuel use is the primary driver of global warming, though the authors note that recent scientific advances allow for more certainty around future projections.
"This assessment shows us in clear scientific terms that climate change is impacting all regions, all sectors of the United States," US president Joe Biden said today. "Not just some, all."
The US now experiences a $1bn weather disaster about every three weeks, compared with once every four months during the 1980s, and is set to warm more on average than the rest of the world as global temperatures continue rising, the report says.
Regional impacts vary. Heightened drought risks in the western US endanger hydropower generation for instance, while sea level rise is projected to be greatest along the US Gulf Coast, threatening much of the country's crude oil production and refining capacity.
US GHG emissions fell by 12pc from 2005-2019, largely because of declining coal-fired generation, but meeting the country's Paris climate agreement commitments and achieving net-zero emissions by 2050 will require emissions to decline by more than 6pc/yr on average. Recent policies like the federal Inflation Reduction Act's clean energy tax credits and new state-level mitigation efforts have helped, but much more action is needed, according to the report.
Existing policies "remain woefully insufficient and incremental," said Kristina Dahl, a report contributor and principal climate scientist at the Union of Concerned Scientists.
Some solutions are already cost-effective, such as building more wind and solar capacity and electrifying more vehicles and heating systems. Less proven technologies like carbon capture may help, according to the report, which also expresses cautious optimism about the voluntary carbon offset market's potential role helping companies meet their climate targets.
The country's exact path to net-zero is still hazy, however, given uncertainty around the role of natural gas-fired generation in a renewables-dominant grid and the extent to which biofuels and hydrogen will help decarbonize sectors that are difficult to electrify. The report notes that most available modeling of a net-zero US involves "substantial" reliance on carbon removals, although it is unclear what strategies, which range from reforestation to industrial direct air capture, will be available at scale.
Though the researchers make clear that the risks of climate change are far greater, the energy transition creates its own risks too. The report notes the high likelihood of rising power demand as more sectors electrify, requiring more investments in energy infrastructure, and the threat of "near-term shortages" of metals and minerals crucial for zero-carbon technologies.
