In last Thursday’s Republican debate, CNN moderator Jake Tapper asked Senator Marco Rubio a question about climate change: would he acknowledge the reality of the scientific consensus on climate change and pledge to do something about it?

Rubio’s answer, and follow-up Friday morning, rehashed what is becoming the standard mantra for climate skeptics in Congress:

  • The climate has always been changing and we don’t know the level of human influence.
  • Regulations and laws to reduce CO2 emissions will harm the economy.
  • Other countries, like China and India, won’t go along with emissions reductions, so U.S. emission cuts will have no impact on rising temperatures.

Let’s examine each argument in turn.

The climate has always been changing and we don’t know the extent of human influence.

In a strict sense, the climate may “always be changing.” While reconstructions of the temperature in the past are difficult, the changes that we have seen recently are rapid and significant, as can be easily seen in the figure below—with significant warming since the 19th century.

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Figure 1: Global temperature [°C] reconstructions from the last 2000 years. The onset of the industrial revolution coincides with a reversal of a cooling trend and a rapid warming. Image Source: IPCC

It is difficult to say exactly how much of the warming we’ve seen since the industrial revolution took off is due to human influence. We can speak somewhat more confidently about the warming over the past half-century, however, given the greater amount of data at hand. Over that period, scientists calculate that at least half and most likely all of the observed warming is attributable to human influence.

Sea level rise follows the same story of unprecedented rapid changes.  Known natural variability and trends cannot explain the increases over the 20th century. That leaves human influence.

Regulations and laws to reduce CO2 emissions will harm the economy

Rubio singled out the EPA’s Clean Power Plan (CPP) as the sort of job killing, economy wrecking program that a Rubio administration would avoid. Now, estimating the cost of the CPP is problematic because the states are charged with writing plans to meet the regulations and states have a lot of discretion in how they go about that. Moreover, cost estimates are highly sensitive to modeling assumption—such as future energy demand and trends in energy production costs—so estimates vary widely.

A recent synthesis finds annual compliance costs averaged over 2020-2030 for the power sector between $4.5 and 33.5 billion annually. This translates into a retail electricity rates increase of between 1.5 and 13 percent. The U.S. Chamber of Commerce estimates compliance costs through 2030 to be $478 billion dollars (at the higher end of the previous range) and emissions reduction costs of $153-163 per ton (well in excess of the Administration’s Social Cost of Carbon).

Given that these regulations are on hold while the courts sort through the legal challenges to the rule, and that states have yet to submit compliance plans, it’s difficult to say whether the costs will be trivial or modest, or something more.

What we do know, however, is that a well-crafted carbon tax can address climate risks without imposing major costs to the economy. This example demonstrates that a $30 carbon tax can decrease GDP by 3 percent or increase it by 1 percent, depending on the mix of tax cuts that are afforded by the carbon revenue. Using the carbon tax to reduce deficits and cut marginal tax rates is the best option for the economy.

The China-and-India Argument

Rubio is right to point out that the United States cannot successfully implement climate policy on its own. Emissions come from all countries, and increasingly, from the developing world. Completely eliminating U.S. emissions tomorrow would lead to small temperature changes at the end of the century, assuming all else would be equal.

But all that means is that U.S. action is entirely necessary in stabilizing atmospheric CO2, and slowing climate change. If climate change is a risk, and emissions reductions justified, then U.S. inaction is unacceptable.

There is also an ethical case to acting on climate policy, despite the emissions of other countries. We know that CO2 emissions trespass on the property rights of others. At this point, the scientific evidence tells us that a ton of CO2 emissions will cause harm. This harm will impact the United States and other nations. Why does the fact that other nations are participating in causing harms excuse the United States? Other nations are emitting CO2 that will cause the United States harm.

That is not to say that the emissions from other countries, including the growing emissions from the developing world, should not be of concern. China does seem to be moving to turn the corner on emissions, but future emissions from India and the rest of the developing world are still an issue.

Historically, the American government has sought to encourage international action via global climate agreements. But even the agreement that came out of COP-21 in Paris appears unequal to the task of managing climate risk.

A unilateral carbon tax, were it applied equally to products coming in at the border, can compel action from other countries based on their own self interest. If energy-intensive goods exported from other countries into the United States were to incur a penalty at the U.S. border, countries that wish to trade in the American market market would have an incentive to price carbon themselves so as to keep the revenue for themselves rather than having it flow into the United States Treasury.

Conservative Principles and the problems of the 21st century

Senator Rubio argued the day after the debate that “We need to take our conservative principles and apply them to the challenges of the 21st century.”

Climate change is definitely a challenge of the 21st century. Conservatives do not need to hold their nose at the science and recycle tired arguments against United States action. A revenue-neutral carbon tax would lessen the risks of climate change, satisfy conservative principles, and demonstrate that the Republican party has smart, market-friendly answers to problems that (rightly) concern voters.