Since well before former President Barack Obama signed onto it as an executive agreement (because he knew the Senate wouldn't ratify it), a number of large American corporations have supported the Paris climate accord. As the time neared when President Donald Trump would announce whether he would keep his campaign promise to withdraw from it, some signed an open letter advising him not to.

Many corporations are household names – Adobe, Blue Cross Blue Shield of Massachusetts, Facebook, Gap, Google, Hewlett Packard Enterprise, Intel, Johnson Controls, Levi Strauss, Microsoft, PG&E (Pacific Gas & Electric) and Unilever among them.

Why would they do that? Let's take their stated reasons one by one.

First, "Strengthening Competitiveness: By requiring action by developed and developing countries alike, the agreement ensures a more balanced global effort, reducing the risk of competitive imbalances for U.S. companies."

The trouble is, Paris, with no enforcement mechanism, doesn't "require" action by any countries, and the "Intended Nationally Determined Contributions" (INDC) by most developing countries committed themselves to no, or next to no, emission reductions. In contrast, the Obama-submitted U.S. INDC committed the U.S. to major reductions by 2025 – long before giant emitters like China and India would even begin any change in their projected emissions growth. (And India demanded over $2 trillion in subsidies or it would do nothing.)

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Second, "Creating Jobs, Markets and Growth: By expanding markets for innovative clean technologies, the agreement generates jobs and economic growth. U.S. companies are well positioned to lead in these markets. Withdrawing from the agreement will limit our access to them and could expose us to retaliatory measures."

But if the "innovative clean technologies" were economically competitive, they wouldn't need the Paris agreement. This is nothing but crony corporatism. Of course anyone can "generate jobs" if governments subsidize them, mandate their products and protect them from competition. But that practice fails the economic test of "That Which is Seen, and That Which is Not Seen." The money to create those jobs is no longer available to create jobs in other industries. That recipients need government to invest in them indicates that investors risking their own money don't consider them a good risk. The result? Misallocated resources and less economic growth than without the program.

Third, "Reducing Business Risks: By strengthening global action over time, the agreement will reduce future climate impacts, including damage to business facilities and operations, declining agricultural productivity and water supplies, and disruption of global supply chains." Yet full compliance with Paris would reduce global temperature at the end of the century by at most 0.17 degree C, far too little to reduce any of the harms mentioned. Meanwhile, the loss of $70 to $140 trillion – the cost of implementation – to the global economy over the period would certainly harm businesses and consumers and reduce the economic growth claimed in their second excuse.

So if none of the state reasons explains why these and many other businesses opposed withdrawing from Paris, what does? A variety of reasons, varying from business to business.

Corporations that stand to benefit from mandates and subsidies to renewable energy – wind, solar, geothermal, and biofuels (and best of all, hydro, but greens oppose new dams) – would naturally object. Exiting Paris puts those mandates and subsidies at risk. For example, Elon Musk, CEO of Tesla and SpaceX, resigned from the president's council of business advisers after Trump's announcement. Duh. He stands to lose big.

Large corporations that see Paris as protection against smaller competition that can't afford the technologies needed to reduce CO2 emissions (e.g., ExxonMobil and Conoco Phillips) would object. It's standard practice for big firms that can stand the cost of regulations to champion regulations that will strangle small competitors.

As Robert Kuykendall of 2ndvote.com points out, some companies see nothing to lose by siding with the environmental left on the issue. It costs them nothing to sign a letter supporting the agreement, and no matter how meaningless the gesture, it signals solidarity with the left and wins a few points. Pure PR, this is called "Greenwashing."

Executives of many of the country's largest corporations identify more now with the "global elite" – the Davos crowd – than with their own stockholders, employees and customers. They see exiting Paris as jeopardizing their cache in those crowds.

Other corporate executives, especially among major international banks and investment firms, are more dedicated to governmental globalism than to American sovereignty. That, as former ambassador to the United Nations John Bolton said on Fox Business News the day Trump announced the withdrawal, is Paris's greatest danger.

"Because of the failure of the predecessor agreements, Kyoto and Copenhagen," Bolton said, "What [organizers] wanted was an agreement on anything, to create the foundation for what they're really interested in, which is more international control over national decision making. This is really a global governance issue, which the Europeans just love, which Barack Obama just loved, which Donald Trump has now rejected. … To me the overarching, ultimately most important, more than constitutional question was, 'Do we govern ourselves here, or are we going to cede governance authority to international organizations?'"

Some business leaders also think – or at least say they think – that by exiting Paris America loses a place at the negotiating table, or loses its leadership in the world, or jeopardizes its mutual defense relationships, etc., all of which were touted as reasons not to reject the Kyoto Protocol but failed to materialize when we did. As Bolton put it, "We've heard these arguments before. In the Bush administration, my first job was to get us out of the 1972 anti-ballistic missile treaty. 'Oh my God!' the Europeans said. 'Oh my God!' Joe Biden, John Kerry, Barack Obama, Chris Dodd said, 'It's the end of international strategic stability.' We got out. Nothing happened. We got out of the statute creating the International Criminal Court. Nothing happened. And nothing will happen here, either. …"

Finally, of course, there are the sincere but uninformed who believe that CO2 emissions are driving catastrophically dangerous warming and that implementing Paris would significantly reduce that at a reasonable cost.

They simply have no idea that the vaunted "97 percent scientific consensus" extends only to the agreement that the world has warmed since the Industrial Revolution (the end of the Little Ice Age) and that human activity has probably contributed "significantly" (which for scientists can mean as little as a few percent). It doesn't extend to the notion that human activity is the majority cause, or that the warming is historically unprecedented or dangerous, or that it's so dangerous as to warrant spending trillions trying to mitigate, money that could be spent instead on providing electricity, pure drinking water, infectious disease control, sewage sanitation, industrialization and lots of other things that lift people out of poverty, disease and premature death and enable them to adapt to any future climate – warmer or cooler.

They don't know that human contribution to global warming is actually real but tiny, (probably so small as to be undetectable).

And they don't know that full implementation of the Paris agreement would, by its own supporters' estimates, reduce global temperature in 2100 by at most 0.17 degree C but would cost roughly $41.2 to $82.4 trillion per tenth of a degree of cooling.

That makes it what the author of "The Art of the Deal" rightly recognized as "a bad deal" – not just for America, but for the world.

Keep these things in mind when climate activists, including some big business leaders, come back demanding that the U.S. re-enter Paris or negotiate some other deal to fight global warming.