• Laura Spinney
• The Guardian, Thursday 23 April 2009
• Article history

Region 486 that unleashed a record flare on the sun. Photograph: NASA/Getty Images

The sun’s activity is winding down, triggering fevered debate among scientists about how low it will go, and what it means for Earth’s climate. Nasa recorded no sunspots on 266 days in 2008 – a level of inactivity not seen since 1913 – and 2009 looks set to be even quieter. Solar wind pressure is at a 50-year low and our local star is ever so slightly dimmer than it was 10 years ago.

Sunspots are the most visible sign of an active sun – islands of magnetism on the sun’s surface where convection is inhibited, making the gas cooler and darker when seen from Earth – and the fact that they’re vanishing means we’re heading into a period of solar lethargy.

Where will it all end? Solar activity varies over an 11-year cycle, but it experiences longer-term variations, highs and lows that can last around a century.

“A new 11-year cycle started a year or two ago, and so far it’s been extremely feeble,” says Nigel Weiss of the University of Cambridge. With Jose Abreu of the Swiss Federal Institute of Aquatic Science and Technology in Dübendorf and others, Weiss recently predicted that the long-term solar high we’ve been enjoying since before the second world war is over, and the decline now under way will reach its lowest point around 2020. Their prediction is based on levels of rare isotopes that accumulate in the Earth’s crust when weak solar winds allow cosmic rays to penetrate the Earth’s atmosphere.

There’s even a chance, says Weiss, that we might be heading for a low as deep as the Maunder minimum of the 17th century. Either side of that trough, Europe shivered through the Little Ice Age, when frost fairs were held on the Thames and whole Swiss villages disappeared under glaciers. So should we expect another freeze?

Those who claim the rise in temperatures we’ve seen over the last century are predominantly the result of intense solar activity might argue that we should, but they’re in the minority. Most scientists believe humans are the main culprit when it comes to global warming, and Weiss is no exception. He points out that the ice remained in Europe long after solar activity picked up from the Maunder minimum. Even if we had another, similar low, he says, it would probably only cause temperatures on Earth to drop by the order of a tenth of a degree Celsius – peanuts compared to recent hikes. So don’t pack your suncream away just yet.

For more than a decade the Global Climate Coalition, a group representing industries with profits tied to fossil fuels, led an aggressive lobbying and public relations campaign against the idea that emissions of heat-trapping gases could lead to global warming.

But a document filed in a federal lawsuit demonstrates that even as the coalition worked to sway opinion, its own scientific and technical experts were advising that the science backing the role of greenhouse gases in global warming could not be refuted.

“The scientific basis for the Greenhouse Effect and the potential impact of human emissions of greenhouse gases such as CO2 on climate is well established and cannot be denied,” the experts wrote in an internal report compiled for the coalition in 1995.

The coalition was financed by fees from large corporations and trade groups representing the oil, coal and auto industries, among others. In 1997, the year an international climate agreement that came to be known as the Kyoto Protocol was negotiated, its budget totaled $1.68 million, according to tax records obtained by environmental groups.

Throughout the 1990s, when the coalition conducted a multimillion-dollar advertising campaign challenging the merits of an international agreement, policy makers and pundits were fiercely debating whether humans could dangerously warm the planet. Today, with general agreement on the basics of warming, the debate has largely moved on to the question of how extensively to respond to rising temperatures.

Environmentalists have long maintained that industry knew early on that the scientific evidence supported a human influence on rising temperatures, but that the evidence was ignored for the sake of companies’ fight against curbs on greenhouse gas emissions. Some environmentalists have compared the tactic to that once used by tobacco companies, which for decades insisted that the science linking cigarette smoking to lung cancer was uncertain. By questioning the science on global warming, these environmentalists say, groups like the Global Climate Coalition were able to sow enough doubt to blunt public concern about a consequential issue and delay government action.

George Monbiot, a British environmental activist and writer, said that by promoting doubt, industry had taken advantage of news media norms requiring neutral coverage of issues, just as the tobacco industry once had.

“They didn’t have to win the argument to succeed,” Mr. Monbiot said, “only to cause as much confusion as possible.”

William O’Keefe, at the time a leader of the Global Climate Coalition, said in a telephone interview that the group’s leadership had not been aware of a gap between the public campaign and the advisers’ views. Mr. O’Keefe said the coalition’s leaders had felt that the scientific uncertainty justified a cautious approach to addressing cuts in greenhouse gases.

The coalition disbanded in 2002, but some members, including the National Association of Manufacturers and the American Petroleum Institute, continue to lobby against any law or treaty that would sharply curb emissions. Others, like Exxon Mobil, now recognize a human contribution to global warming and have largely dropped financial support to groups challenging the science.

Documents drawn up by the coalition’s advisers were provided to lawyers by the Association of International Automobile Manufacturers, a coalition member, during the discovery process in a lawsuit that the auto industry filed in 2007 against the State of California’s efforts to limit vehicles’ greenhouse gas emissions. The documents included drafts of a primer written for the coalition by its technical advisory committee, as well as minutes of the advisers’ meetings.

The documents were recently sent to The New York Times by a lawyer for environmental groups that sided with the state. The lawyer, eager to maintain a cordial relationship with the court, insisted on anonymity because the litigation is continuing.

The advisory committee was led by Leonard S. Bernstein, a chemical engineer and climate expert then at the Mobil Corporation. At the time the committee’s primer was drawn up, policy makers in the United States and abroad were arguing over the scope of the international climate-change agreement that in 1997 became the Kyoto Protocol.