The Thunder Over New Hampshire air show marked the first appearance of the F-16 Thunderbirds at the Pease Air National Guard base in a decade.

For all its heart-pounding entertainment value, the air show that opened this year on the 20th anniversary of the Sept. 11 terrorist attacks is emblematic of the challenges American policy makers face in 2021 — issues that range from defense readiness to climate change to environmental remediation.

The jet fighters taking center stage this weekend were developed decades before 9/11, in response to what military planners viewed as a Cold War threat from advanced Soviet MIG jet fighters.

While aviation experts agree that the U.S. succeeded in our development of the preeminent Air Tactical Fighter, achieving superiority in air-to-air and air-to-ground combat, the decades-long Afghan conflict is a reminder that air power goes only so far.

Becca Wasser and Stacie Pettyjohn, analysts at the Center for New American Security and co-authors of “The Air War Against the Islamic State,” write that American air power could not have altered the outcome of the 20-year Afghan conflict.

“Although a much more aggressive air campaign launched earlier could have blunted the Taliban’s offensive, alone it would not have defeated the Taliban. As the war against ISIL demonstrated, American airpower can halt an offensive, but it alone cannot liberate captured territory,” they wrote.

In the two decades since 9/11, much has changed in the world. Navy Secretary Carlos Del Toro reminded us of this during a visit to the Portsmouth Naval Shipyard last week.

“The threats on the horizon are very real today,” he said.

Del Toro listed Russian aggression in the Arctic and Mediterranean — “right up to our own Atlantic shores” — and said that rogue actors and terrorists continue to threaten the Gulf states and sea lanes all around the world. He named China as our “pacing threat,” which is a Pentagon-way of saying they are the only country that can challenge the U.S. militarily, economically and technologically.

Sen. Jeanne Shaheen (D-N.H.), who sits on the Senate Armed Services and Appropriations committee, talked at the shipyard about how the $1.7 billion multi-mission dry docks will permit the simultaneous refurbishment of nuclear attack submarines.

“It’s essential that we continue to prioritize and secure consistent, predictable funding for these projects,” she said.

Congressional representatives and policy makers in 2021 are increasingly cognizant of the other “elephant in the room” — the military’s dependence on fossil fuels, the challenge of energy efficiency and the threat of climate change.

The military is the single-largest institutional consumer of petroleum fuels, according to a 2019 report by the Watson Center for International and Public Affairs.

Following orders from President Joe Biden, Secretary of Defense Lloyd Austin earlier this year said the Pentagon “will immediately take appropriate policy actions to prioritize climate change considerations in our activities and risk assessments, to mitigate this driver of insecurity.”

The air show on the site of the former Pease Air Force Base is emblematic of another challenge: environmental compliance and the costs associated with past environmental pollution.

The Department of Defense, Pease Tradeport businesses and the surrounding communities are dealing with the contamination of groundwater from chemical agents used in firefighting foam.

Shaheen knows firsthand the costs associated with deferred maintenance and other neglect. She sits at the center of competing national and local priorities — at a time when the stakes are high and the costs astronomical.

This may be best illustrated by two recent Senate actions — consideration of the National Defense Authorization Act (NDAA) and Senate passage of the $1 trillion infrastructure package.

In the “markup” of the NDAA, the Armed Services Committee proposed defense spending next year of $777.9 billion, $25 billion more than Biden asked for.

Shaheen said Wednesday she supports the increase. It came on a near-unanimous, bi-partisan vote. Only Massachusetts Sen. Elizabeth Warren voted “nay” on the increase.

A growing defense budget, juxtaposed against the need for action on climate, energy efficiency and environmental sustainability, may seem paradoxical.

But it’s worth noting that the Union of Concerned Scientists said 2021 marked “the fourth year in a row in which both sides of the aisle have come together to pass climate change provisions in the NDAA.” Congress seems on track to do it again.

The broad outline of 2022 Pentagon spending keeps or grows funding related to uncovering the potential health effects related to per- and polyfluoroalkyl (PFAS) contamination in response to chemical exposure and remediation of polluted sites. It also authorizes $6.57 billion for the Department of Energy’s defense environmental cleanup activities, which could apply to both Pease and the Portsmouth Superfund sites.

Twenty years ago, the “guns versus butter” calculus turned on long discussions about tax revenues, deficit spending and curbing federal waste.

As the jets thunder over Pease this weekend, 2021 is looking like a year in which a bipartisan group of senators may hold sway over an enormous investment in guns and butter.