Dear Dr. Hansen:

An old engineer’s dictum says “fast, cheap, good: pick two.” Unfortunately, and I’m sure completely contrary to your intention, your solution to global warming favors “cheap” over fast.

Energy efficiency, renewable energies, and a “smart grid” deserve first priority in our effort to reduce carbon emissions. With a rising carbon price, renewable energy can perhaps handle all of our needs. However, most experts believe that making such presumption probably would leave us in 25 years with still a large contingent of coal-fired power plants worldwide. Such a result would be disastrous for the planet, humanity, and nature.

Fourth generation nuclear power (4th GNP) and coal-fired power plants with carbon capture and sequestration (CCS) at present are the best candidates to provide large baseload nearly carbon-free power (in case renewable energies cannot do the entire job).

OK, this begs the question of why depending on efficiency, carbon negative forestry and agriculture, and renewables would leave us “in 25 years with still a large contingent of coal-fired power plants worldwide.”

We certainly have the physical capacity to build wind and solar generators that could provide all our power. Archer and Jacobson, perhaps the world’s leading experts on wind potential, estimate that wind energy at 80 meters in commercially developable sites alone could could supply [PDF] five times the world’s current energy demand. Note the emphasis: That is not five times world’s current electricity consumption, but five times total world energy consumption, including cars and factories and non-electric heating1. Similarly, solar thermal power plants of the type already running in U.S. deserts2 can provide the world’s entire energy needs [PDF] from less than 1 percent of total desert land3. Those are only two possibilities, albeit the ones with the biggest potential with today’s technology.

Is it power variability that worries experts? Jacobson and Archer have documented that connection via long distance transmission can reduce [PDF] that variability4. More to the point, data from that study show that much of that variability consists of reductions in available power of relatively short duration5 [PDF], which could be bridged by comparatively small amounts of storage in flow batteries or (in the case of solar thermal generation) via thermal storage. Keep about two thirds of existing hydro, and add as much additional geothermal electricity as makes sense with today’s technology. Add inexpensive, not overly efficient natural gas turbines for occasional use, providing less than 2 percent of total power, and you will end up with a reliable grid, with less than 2 percent of today’s emissions per kWh.

Is it cost that worries you? Without technical breakthroughs, and if we don’t count social costs, energy generated in this way is more expensive than today’s grid. But we also know that a great deal of today’s energy is thrown away. There are numerous cost-effective ways to get more GDP out of a kWh of energy. So if we combine efficiency improvements, the net total price of energy will be around what it is now. The average household may pay more per kWh for electricity, but the average electric bill won’t rise much, if at all.

Further, social benefits other than fighting climate chaos will more than make up for any difference. For example, greening commercial, retail, and some industrial buildings will improve productivity [PDF] and add huge amounts to our GDP6. Similarly, as we reduce air pollution from power plants, factories, and ground transport, we’ll receive tremendous additional value from improvements in public health. I’ve written extensively about policies that will enable us to implement this transition at minimal cost and capture some of the immediate social benefits to reduce immediate net costs below what we pay today.

None of this is technically iffy. Wind generators are manufactured and installed every day. Concentrating Solar Power farms using mirrors to concentrate energy and drive heat engines currently exist, and more are being built every day. Flow batteries and high temperature thermal storage are commercial products. Long distance HVDC transmission lines have been used all over the world for decades and are being built extensively in China today. The costs of all these technologies are well documented, as are costs for efficiency technologies.

As the world’s leading climate scientist, you know the patterns and parameters for available solar and wind energy can be estimated, with significant but known margins of error. If you look into it, I think you will find the social paybacks can also be documented rigorously. Because of such paybacks, I think you will find that phasing out emissions actually increases future GDP more than continuing to emit — even before climate effects are considered. And all this assumes no technical breakthroughs, which as we know is unduly pessimistic.

So why flounder about with fourth-generation nuclear power and “clean coal”? Yes, with sufficient effort we might be able to make breakthroughs in those fields in fewer than 30 years. But we might not, and even if we do, we have no idea what the cost will be. I’m not opposed to research in those areas, but to make such research one of four major planks in fighting global climate disruption seems like a bad choice.

Our primary focus must be implementing technology we already have. Even if major breakthroughs occur, it’s unlikely they will ever provide power as cheaply as dirty coal plants already built. As a safety valve, funding a speculative gamble seems like a poor choice. Breakthroughs or no, nothing will allow us to avoid doing the hard political work of investing large amounts of money to phase out emissions.

It seems odd to try to find a technology that will persuade the Chinese to stop burning coal. The Chinese have already advocated for a path to global emission reductions. They want rich nations, who are responsible for most historical emissions and still have the highest per capita emissions, to pay a substantial amount toward the cost of a green path for poor and developing nations. They suggest around $300 billion annually. That’s about a third of the current U.S. military budget, to be paid by all rich nations combined, to all poor and developing nations combined. (Thus the U.S. share would be substantially less than $300 billion annually.)

But of course, it is not just China you are worried about.

You’ve probably noticed that nobody is shutting down coal plants. You probably worry that shutting down coal isn’t technically feasible, and moreover that what we could do with current technology is not politically feasible.

But what is necessary is also politically feasible if a movement advocates for it. Put in place public investments to encourage key infrastructure: smart grids, long distance transmission, storage, electric cars, and efficiency improvements in buildings. Put in place regulations that encourage efficiency and a transition to renewable energy. Yes, put in place a refundable carbon tax. Ultimately, negotiate a deal whereby
rich nations pay poor ones to lower their emissions.

Yeah, this is politically difficult. But so is any path to seriously tackling climate chaos. And unlike end-of-tailpipe solutions — which we don’t currently have in any case — an efficiency-and-renewables scenario offers a bigger GDP than business as usual, even before global warming costs are considered. Positive externalities more than make up for the costs.

When it comes to research, sure, put some into nuclear and decarbonization of emission streams. The latter will likely be necessary even when our economy reaches near-zero emissions, if only to transition to carbon negativity.

But don’t forget there are research investments with nearer short-term payoffs. Various techniques for making less expensive and simpler concentrators could lower the cost of solar thermal tremendously. Various means of lowering the cost of solar thermal storage from $35 per thermal kWh equivalent to $10 or $15 can be implemented in the short term. Similarly, adiabatic compressed air storage has tremendous long-term potential, as do other methods of electricity storage. There are a number of methods of improving blades, gearing, and control for wind generators, and the long-term potential for flying wind generators.

Please don’t drain all the money for improving renewables into fourth-generation nuclear power and “clean coal.”

Maybe we will get power too cheap to meter some day, either in nuclear form or from various breakthroughs in renewable energy and storage. But I’d hate to have the survival of our civilization depend on that when technologies available today lower emissions at a reasonable cost, certainly at a cost much less than the destruction of unmitigated climate chaos.

Kyoto and other attempts to phase out emissions have failed not because the technological barriers are too high, but because emissions reduction is fundamentally an infrastructure problem that has to be tackled via public investment and regulation — the way infrastructure always is. We did not get railroads, highways, airports, water ports, electric lines, sewer systems, clean drinking water, or the internet through “price signals.” None of these would have happened without public investment, some in the form of grants of land and right of ways, some in direct public ownership. None would have happened without regulations that created an environment friendly to technologies we wanted to encourage.

Getting price signals right can complement investment and regulation. Such a three-pronged policy approach can move us to zero and even negative emissions at the speed you advocate. But the public investment portion has to be sufficiently large, and the regulations sufficiently stringent, before pricing will be effective.

When investment, regulation, and pricing are in place, research and development can serve as reinforcement — not as a safety net that tries to bypass politics.


1 Cristina L. Archer and Mark Z. Jacobson, “Evaluation of Global Wind Power,”. Journal of Geophysical Research – Atmospheres 110, no. D12 30 Jun 2005, American Geophysical Union, 20-Jan-2008, D12110 DOI:10.1029/2004JD005462.

2 The Plant | Nevada Solar One,, accessed 04 Jan 2009.

3 Dr. Gerhard Knies, “A Brief Overview on Global Energy, Water and Carrying Capacity Perspectives,” Clean Power From the Deserts: The DESERTEC Concept for Energy, Water and Climate Security, ed. Club of Rome, Oct 2008), 3rd Edition. Oct 2008. Trans-Mediterranean Renewable Energy Cooperation 04/Jan/2009

4 Cristina L. Archer and Mark Z. Jacobson, “Supplying Baseload Power and Reducing Transmission Requirements by Interconnecting Wind Farms,”. JOURNAL OF APPLIED METEOROLOGY AND CLIMATOLOGY 46, no. 11 Nov 2007: 1701-17, American Meteorological Society, 18/Jan/2008

5 Willet Kempton and Amardeep Dhanju, “Electric Vehicles with V2G Storage for Large-Scale Wind Power,”. Windtech International Mar 2006, (accessed 27 Dec 2004) <;. Figure 2. (Note: the graph is based on unpublished data from Archer and Jacobson’s studies.)

6 Mark Palmer and Alicia Mariscal, Green Buildings and Worker Productivity: A Review of the Literature, Aug 2001). Aug 2001. San Francisco Department of the Environment

Gregory H. Kats, Green Building Costs and Financial Benefits. October 2003. Massachusetts Technology Collaborative State Development Agency for Renewable Energy and the Innovation Economy., .p6., accessed 12/29/2008.