I was dismayed when I read Terry Tamminen's article "Divest or Double Down?" Then, when I learned that he was part of a University of California task force that will be making a recommendation to the U.C. Regents on whether the University should divest from fossil fuels this September, I became alarmed.

Tamminen clearly is aware that climate change is going to be very costly with regard to food production, public health and extreme weather. However, when he lumps climate change together with other "worthy causes," he demonstrates his lack of understanding about its dire urgency. The call to divest from fossil fuel is far more than a "worthy cause," it is a call to prevent climate catastrophe.

Global warming is the most serious threat humanity has ever faced. If we allow fossil fuel companies to continue business as usual, we will exceed our carbon budget -- the amount of carbon we can emit into the atmosphere before exceeding the 2 degree Celsius climate tipping point -- in 30 years. With catastrophe looming, we have neither the time nor the resources to push fossil fuel companies to do the right thing through shareholder engagement -- a tactic that has proven ineffective in transforming these stalwarts of the old energy order. The money the industry spends on alternative energy is a pittance, and there is little evidence that it has improved its sustainability practices. Even though the industry must keep 80 percent of its current reserves underground to preserve the planet for our children and grandchildren, ExxonMobil alone spends $100 million every day exploring for new oil and gas to burn.

Fossil fuel companies exert enormous power. They are aggressively and dishonestly attacking the renewable energy sector by manipulating states to repeal their Renewable Energy Standards laws, thereby obstructing the transition to clean energy. We already have in the United States credible plans and viable technology to power our economy with 100 percent renewable energy. However, because of the industry's choke hold on politicians on both sides of the aisle, the political will to transition to clean energy is lacking. It is therefore imperative that we, the people, through our public institutions, send a message to the fossil fuel industry that we want to preserve the planet and, likewise, our portfolios.

Portfolios invested in fossil fuel are at great risk, but Tamminen turns a deaf ear to the advice of financial experts. For example, Bevis Longstreth, former commissioner of the U.S. Securities and Exchange Commission and an expert on fiduciary duty, presents a strong financial case for divesting from fossil fuel companies. He says future prospects for these companies are suffering and will continue to suffer from four rapidly evolving developments: governmental restrictions; advances in alternative sources of energy for power resulting in falling demand for coal, oil and natural gas; a rapidly growing grass-roots movement that demands "cessation of CAPEX on exploration and development of more fossil fuel"; and the growing stigmatization of fossil fuel companies in the mind of the public.

Large financial institutions including HSBC, Citibank, the International Monetary Fund and the World Bank (hardly radical outfits) are also aware of the looming "carbon bubble" -- vast fossil fuel reserves that cannot be burned if we are to avert environmental catastrophe -- which dwarfs the housing bubble that nearly brought down the U.S. economy. Investors lost $5 trillion when the dot.com bubble burst and $7 trillion when the housing market collapsed. Potential losses from an exploding carbon bubble could wipe out as much as $28 trillion in shareholder value and send the global economy into an unprecedented tailspin.

Nobody knows the economic risks of the climate crisis better than Henry Paulson, the Republican Secretary of the Treasury when the credit bubble burst. Paulson recently warned:

We're making the same mistake today with climate change. We're staring down a climate bubble that poses enormous risks to both our environment and economy. The warning signs are clear and growing as the risks go unchecked....This is a crisis we can't afford to ignore....We can see the crash coming, and yet we're sitting on our hands rather than altering course. We need to act now....

I would argue that with warning lights and sirens flashing and blaring, continued investment in the fossil fuel industry is itself a breach of fiduciary responsibility. By divesting from fossil fuel companies, fiduciaries of endowments and pension funds will protect their portfolios from what Dr. Celine Herweijer, a partner in PricewaterhouseCoopers, has called "the mother of all risks." Helping to protect current and future generations of students and the greater public, to which the UC Regents owe their fiduciary duty, would be a welcome collateral effect.