An untimely confluence of bad weather, flawed energy policies, low stockpiles and voracious growth in Asia's appetite has driven international spot prices of coal up by 50 percent or more in the past five months, surpassing the escalation in oil prices.

The signs of a coal crisis have been showing up from mine mouths to factory gates to living rooms: As many as 45 ships recently were stacked up in Australian ports waiting for coal deliveries slowed by torrential rains. China and Vietnam, which have thrived by sending goods abroad, abruptly banned coal exports, while India's import demands are up. Factory hours have been shortened in parts of China, and blackouts have rippled across South Africa and Indonesia's most populous island, Java.

For their parts, mining companies are enjoying a windfall. Freight cars in Appalachia are brimming with coal for export, and old coal mines in Japan have been reopened or expanded. European and Japanese coal buyers, worried about future supplies, have begun locking in long-term contracts at high prices, and world steel and concrete prices have risen already, fueling inflation.

In the United States, the boom in coal exports and prices has helped lower the trade deficit, which declined last year for the first time since 2001. The value of coal exports, which account for 2.5 percent of all U.S. exports, grew by 19 percent last year, to $4.1 billion, the National Mining Association said. An even bigger increase is expected this year.

Big swings in the prices of coal and other commodities are common. And even though the price of coal has slipped slightly in recent weeks, many analysts and companies are wondering whether high prices are here to stay. As increasing numbers of the world's poor join the middle classes, hooking up to electricity grids and buying up more manufactured goods, demand for coal grows. World consumption of coal has grown 30 percent in the past six years, twice as much as any other energy source. About two-thirds of the fuel supplies electricity plants, and just under a third heads to industrial users, mostly steel and concrete makers.

Meeting rising demand will prove difficult. To maintain its role as the world's producer of last resort, the United States will need to make major investments in mines, railways and ports.

''We're at a point where we're running through the capacity,'' said David Khani, a coal analyst at Friedman, Billings, Ramsey Group. He compares the coal market to the oil market. For coal, he added, ''it is unprecedented.''

If high prices last, that would raise the cost of U.S. electricity, half of which is generated by coal-fired powered plants.

Expensive or not, coal is almost always dirtier to burn than are other fossil fuels. Although its use accounts for a quarter of world energy consumption, it generates 39 percent of energy-related carbon dioxide emissions. Climate change concerns could lead to legislation in many countries imposing higher costs on those who burn coal, forcing utilities and factories to become more efficient and curtail its use. Climatologists warn that without technology to capture and store carbon dioxide emissions, burning more coal would be disastrous.

China's energy appetite

China, the world's largest consumer of coal, is burning through more than the United States, European Union and Japan combined. And its consumption is increasing by about 10 percent a year. In 2006, it installed power plants with more capacity than all of Britain.

China has vast coal resources, but its growing appetite has outstripped production. In January 2007, it imported more coal than it exported for the first time, according to government figures.

Logistics compound China's coal woes. The biggest deposits lie inland and in the north, while most of the fast-growing industries are in the south and along the coasts. Transporting all that coal strains the railways, half of which are devoted to coal transport.

Strong coal demand has created incentives for small illegal coal mine operations that are extremely dangerous and highly polluting. The government has shut down 11,155 such mines since 2005, further crimping supplies.

Developing countries aren't the only ones using more coal. Throughout the 1980s and 1990s, British coal consumption declined as new sources of oil and natural gas were discovered in the North Sea. However, the trend has reversed, and coal consumption has climbed steadily over the past six years, including a 9 percent jump from 2005 to 2006. Coal has surpassed gas once again as the leading fuel for electricity plants.

Mine production capacity declined during the '80s and '90s ''dash for gas.'' Now Britain imports coal from Russia, Australia, Colombia, South Africa and Indonesia.

Floods reveal supply flaws

Sometimes it takes an act of nature to uncover human and policy flaws. The fragile balance of coal supplies in Asia has been exposed this winter to flash floods and torrential rains in Asia's top coal-producing nation, Australia. The floods caused six big coal producers in Queensland to declare ''force majeure,'' a contractual option that allows them to miss coal deliveries because of events outside their control. The companies include Rio Tinto (owner of Kennecott Utah Copper) , BHP Billiton and Xstrata.

Australia's problems have contributed to a surge in Asian spot prices, meaning prices for immediate delivery, for coking coal, used for iron and steel production. They are running at three times the current contract price of $98.

South Africa, which might ordinarily have come to Asia's rescue, was wrestling with its own supply problems. The state-owned utility, Eskom, let coal reserves dwindle, and power plants simply ran out. Power outages crippled the country. Heavy rain also dampened coal piles, making it harder to burn the tiny reserves efficiently.

Rolling power outages forced the mining industry to shut down for several days. Amid this political debacle, Eskom vowed to replenish its coal stockpiles, a push that will eat into supplies available for export.

Australia's gridlock also coincides with deep cuts in coal exports by Vietnam, a key supplier to Japan and China. Vietnam will raise tariffs on coal exports to slash them by about a third this year. The goal is to keep coal at home for domestic needs. Last year, Vietnam exported 32.5 million tons of its total production of 41.2 million tons.

Mines in high gear

For mining companies, the coal crisis is a bonanza.

The price hike has revived long-neglected mines in Hokkaido, a region in northern Japan that has been producing coal for more than a century. As global coal prices have more than doubled, the Japanese mines have suddenly become competitive and they are attracting the attention of utilities and companies that use coal for power.

Hokkaido Electric Power Co. this year doubled its coal order from the Hokkaido mines, from 500,000 to 1 million tons. The mines cannot produce enough coal to meet new requests.

In the United States, it is getting harder to license and borrow money to build new coal plants. But Peabody Energy's chief executive Gregory Boyce says foreign demand will sustain mining output. ''Coal is the sustainable fuel best able to close the gap of growing demand versus scarce and expensive alternatives,'' he said at a conference last month.

Khani, the Freidman Billings Ramsey analyst, said that ''coal use has expanded beyond steam and steel into coal-to-liquids in China and coal-to-chemicals,'' which he said would link coal prices to oil as well as natural gas. Given recent oil price levels, that could mean higher prices for coal, too.

That could slow U.S. and worldwide economic growth and contribute to a renewed bout of stagflation. Rising commodity prices are ''producing real limits on the future of economic growth in the U.K. and overseas,'' said Shaun Chamberlin, a specialist in energy and climate change at the Lean Economy Connection, an research institute in London. ''In terms of industry, we're running out of ways of generating energy. We've jumped around from one energy source to another, and now we're running out.''

All this is especially bad news for those worried about climate change. Germany, for example, is caught between its pledge to eliminate nuclear power and its pledge to slash carbon emissions. Because nuclear energy accounts for a quarter of the country's electricity needs, utilities have filed applications for permits to build two dozen coal-fired plants over the next few years.

''You reach a point where people say you have to stop burning coal,'' said Per Nicolai Martens, director of the Institute of Mining Engineering at the Aachen Technical University in Germany. ''But when you reach that point, you are forced to ask the question of what happens when you shut it off?''