Hansen’s Q’s & A’s and what can be done.

Questions and Answers (incomplete)
1. Less than 350 ppm: Are you saying that the optimum level of atmospheric CO2, for humanity and nature, is 350 ppm?

The optimum amount of atmospheric CO2, or, better, the acceptable range, will depend upon how well we do in reducing other greenhouse gases. And it depends upon the magnitude of negative human-made climate forcings due to changes in atmospheric aerosols and surface reflectivity, which are not yet well-defined.
The important point is that we must halt and reverse the growth of CO2, taking it back to the 350 ppm
level and probably lower. That conclusion already tells us that we must fundamentally change ‘business as-usual’ energy policies now. The most important implication: we must phase out coal emissions as soon as possible.
In retrospect, we should not have been surprised that the appropriate ‘target CO2′ is less than 350
ppm. After all, CO2 is the single largest climate forcing (perturbation of the planet’s energy balance,
which tends to alter global temperature) and humanity and natural ecosystems adapted to the climate
produced by the pre-industrial ~280 ppm CO2 amount that existed for the past 10,000 years.
Civilization’s infrastructure was built for the climate zones of the Holocene, and the infrastructure
depends on the stable sea level of the past several thousand years.
If we were starting ab initio, with a choice of climates, would we have chosen the Holocene? That’s a
rhetorical question, but the Holocene is an excellent choice. It is warm enough to keep ice sheets off
North America and Eurasia, but cool enough that we have mountain glaciers all around the world (as well as ice sheets on Greenland and Antarctica). Mountain glaciers are very useful, because they supply fresh water for rivers through the summer and fall, after snowmelt is long gone. An alternative would have been CO2 of say 500 ppm, which would yield little or no ice on Earth and thus a more stable sea level, but a less diverse and interesting planet.
2. China and India: What hope is there of solving the problem with emissions from China and India increasing so rapidly?

No. In the long run, the level that we need to aim for is probably less than 350 ppm. But for the time
being all that we need to know is that we must adopt policies that take the planet’s atmosphere back to a CO2 amount of 350 ppm or less.

Even though China has passed the United States in current emissions, the U.S. is responsible for more
than three times the amount of fossil fuel CO2 in the air today than any other country. Thus the United
States has a responsibility to take a leadership role in finding ways to reduce emissions.
Besides, early development of technology is in the best economic interest of the U.S. China and India will surely become part of the solution, because they have more to lose from climate change than most countries. They also have more to gain from clean energies, as they presently have great pollution from use of fossil fuels. And these countries have the ability to move rapidly to new technologies, in part because they have less invested in old technologies.
I have no doubt that China and India will move smartly into the era beyond fossil fuels, once the path
is better defined. The United States should be leading the way in defining a viable path.
3. Coal and R&D program for nuclear power: Why emphasize coal? Isn’t coal use declining?
No. Coal is the largest source of human-made CO2 in the air today, as much as oil and gas combined.
In addition, coal use has been accelerating in the past several years, while supplies of oil are more limited.
Oil emissions will inevitably decline. It does not make sense to go to extreme environments to try to
squeeze every last drop of oil out of the Earth.
Coal is also the dirtiest of the fossil fuels, and is a primary cause of air pollution including
particulates, mercury and radioactive materials. At present there is no such thing as “clean coal”.
 Even if capture and sequestration of CO2 and other pollutants becomes technically feasible (commercial scale operations of carbon capture seem to be at least a decade away) the great environmental damage associated with mountain-top removal to mine coal would remain.
In my opinion the best place for coal is to leave it in the ground. We should move on to renewable
energies and improved energy efficiency. Coal supply is finite, so we must move to other fuels
eventually. Why not do it sooner, rather than later, thus preserving a planet similar to the one on which civilization developed during the past several thousand years?
We should also have a strong R&D program, on an emergency basis, to evaluate the potential of next
generation nuclear power, specifically breeder reactors that can burn nuclear waste, thus minimizing
several problems that have been associated with nuclear power. Nuclear power may be required for baseload electrical power to allow countries such as China and India to phase out coal emissions over the next few decades. The aim should be to establish a standard safe design, one allowing modular factory construction and standard operating procedures, thus allowing rapid deployment, avoiding the long delays and price increases of the current approach.
4. Greenwash: Haven’t most governments already recognized the global warming problem and begun to take actions to solve the problem?

These governments are kidding themselves and the public. Similarly, there are plans in many states within the United States for new coal-fired power plants. And several countries, including the U.S. and Japan, have plans to make submarine methane hydrates a commercially viable energy source within a decade – if left unchecked this could unlock a vast reservoir of fossil CO2.
The best hope for leadership on this issue at the moment appears to be the United Kingdom, where
the government is debating their policy regarding coal, raising the possibility of a moratorium on new
coal plants. However, it would be necessary for the European Union and the Untied States to be brought on board quickly, and to move from a moratorium to phase-out of existing coal plants. The difficulty is that there are powerful coal industries in all of these countries. The governments in these countries do not seem to grasp the urgency of the situation, and they do not take a long-term view of the energy and economic situations.
5. Inter-generational inequity and injustice: when will climate change be a problem?
Some climate impacts are already becoming apparent, including an increase of extremes of the water
cycle (heavier rainfall and floods, but also more intense dry periods and fires), melting of mountain
glaciers with effect on fresh water supplies (once the glaciers are gone, potentially within a few decades if CO2 growth is not halted, the rivers will tend to run dry in the summer and fall), expansion of the subtropics (affecting the Southern United States, the Mediterranean region, Australia and Africa), and shifting of climatic zones (affecting the health of some vegetation and human health through spread of disease vectors).
Such climate impacts will increase over the next few decades, affecting the people who are causing emissions as well as future generations.
However, the most serious effects will be visited upon the young and the unborn, the generations that
bear no responsibility for the problem. The most important effects, I believe, will be those that are
irreversible for all practical purposes, specifically (1) extermination of species, and (2) ice sheet
disintegration and sea level rise. If we continue business-as-usual energy policy, using more and more fossil fuels, it is likely that we will have:
(1) rapid climate change that will combine with other pressures on species to cause the rate of
extinction of plants and animals to increase markedly, leading in some cases to ecosystem collapse,
snowballing extinctions, and a more desolate planet for future generations.
(2) meter-scale sea level rise this century, and ice sheets in a state of disintegration that guarantees
future sea level rise in the 10-meter-scale, with a continual reworking of future global coastlines out of humanity’s control.
6. Protests against government inactions: what is appropriate?

No. Governments, utilities, and the fossil fuel industry have presented public faces acknowledging
the importance of climate change and claiming that they are taking appropriate actions. Yet the facts
contradict their claims. Even the apparently “greenest” countries, such as Germany and Japan, are
making plans to construct new coal-fired power plants.

Protests analogous to the ones at Kingsnorth in the United Kingdom
( and Wise County Virginia
( are likely to increase as young
people become aware of the implications of continued coal burning. When does it become appropriate for young people to become fed up with the lack of appropriate government action?
My recommendation has been that young people spend maximum effort now on the democratic
process, affecting upcoming elections on all levels, and then, after the election, demanding that those
elected deliver on their promises. I have cooperated with the (nominally non-partisan) PowerVote,
Virginia Powershift, ReEnergize Iowa,,, for example.
I have also drawn attention of youth to the Student Environmental Action Coalition (SEAC).
Applications for training and participation in their programs can be found at (