It can be difficult to keep a sense of perspective in the midst of a crisis. Yet this is what the Japanese earthquake, tsunami and resulting nuclear accidents demand. There is no doubt that the explosions and radioactive releases at the stricken Fukushima Daiichi plant represent the worst nuclear disaster since the explosion at the Chernobyl power plant in Ukraine in 1986. However, that does not mean the correct response is panic. At the time of writing, the most likely long-term outcome remains that neither the public nor the plant workers will die or be harmed from the doses of radiation that they have received.

You could argue that, in the context of a tsunami that may have killed 10,000 people or more, the overwhelming media focus on the Fukushima crisis is disproportionate. But the Japanese government is in a no-win situation: if Prime Minister Naoto Kan tries to calm public fears, he will be accused of conspiring in a cover-up. However, by telling people to stay indoors, not to drink tap water and to evacuate from all areas within a 30-kilometre radius around the Fukushima plant, the government has risked triggering panic at a time when rescue teams are still uncovering survivors and when those who have lost their homes need to be cared for and fed.

It is far too early to make any meaningful assessment of the long-term effect of the nuclear accident. Explosions have destroyed the outer walls of two of the reactor buildings. Over in another building, a fire has been reported near a cooling pond that lost its water, while the containment vessel housing the reactor core of one of the units may have been damaged. The last two incidents seem to have released sufficient radioactive material to pose a potential health hazard for those close by. At the time of writing, the situation is not yet under control and may still deteriorate.

But even a total meltdown would be much less deadly than at Chernobyl, where the reactor was still operating when it blew up, spreading burning and radioactive debris and dust over wide areas. Moreover, Soviet-era design flaws in the Ukrainian reactor meant that it had a "positive void coefficient": a loss of coolant would speed up the reaction and allow it to run out of control, which was what happened when the operators ran an ill-advised test on 26 April 1986.

If the crisis in Japan leads to a large-scale shift in attitudes against nuclear power, the outcome will be a worsening of human impact on the
environment. Japan is a good example of why fixing global warming without increased use of nuclear energy is as good as impossible: the country has little resources of solar or wind power, and is heavily dependent on imported fossil fuels. Coal and nuclear each meet about 25 per cent of Japanese energy needs.

Any running down of nuclear power over the short or medium term will lead to higher use of coal and gas, greater greenhouse emissions and an intensifying contribution to global warming. Increased renewables and efficiency could alter this trajectory by a few percentage points, but that is all. Japan is already trying to extricate itself from the Kyoto Treaty on climate change - without recourse to nuclear generation, it will struggle to meet the existing targets, let alone any new ones.

Disaster zone

It is important to bear in mind that all energy sources carry risks. The BP disaster in the Gulf of Mexico last year killed 11 workers and polluted a large area of ocean and coast, yet the US government is leasing new areas for offshore drilling. Natural-gas infrastructure occasionally blows up, sometimes killing civilians (most recently in Italy in 2009, when a train carrying liquefied natural gas derailed and exploded), while thousands are killed each year in coal-mine disasters. Hydroelectric dams are also vulnerable to earthquakes and risk causing inland tsunamis if they burst. Even wind turbines may need to be surrounded by exclusion zones, because of the possibility of ice falling from their blades and other hazards.

Nuclear power has so far maintained an enviable safety record, even during accidents: Three Mile Island, in Pennsylvania, US, which resulted in a partial meltdown in 1979, released very little radiation and had no impact on the health of surrounding populations.

None of this should be misinterpreted as an argument for complacency in nuclear engineering. Newer reactor designs include even more passive safety elements, and no doubt grave lessons will be learned from the events in Japan. It is notable that the Fukushima plant, which is 40 years old, should have been shut down, but had its lifetime extended because of the demand for electricity.

Similar extensions to older reactors have been considered or granted in Germany, the UK and Sweden. Why policymakers, anti-nuclear campaigners and the general public prefer to keep older and less safe reactors open well past their design lifetime rather than allow the construction of new plants is a mystery.

The Japanese nuclear crisis comes at a time when many were beginning - in the light of climate change - to re-examine their opposition to civil nuclear power. Anti-nuclear campaigners may feel vindicated, but they should be careful what they wish for: if we abandon nuclear, prepare for a future of catastrophic global warming, imperilling the survival of civilisation and much of the earth's biosphere.