Nearly 200 world leaders - among them the heads of state of the two countries that produce the most carbon dioxide emissions, China and the United States - made strong statements to open the continuing climate control summit in Paris last week. But any accord reached before the meeting ends Friday will likely lack the thunder of their speeches.

Even before the 21st Conference of Parties (COP21) began, scientists warned that the United Nations Framework Convention on Climate Change was setting the bar too low. U.N. Secretary-General Ban Ki-moon voiced similar pessimism, saying the reductions in carbon dioxide emissions being pledged by each country were too modest.

Their pledges, known as "Intended Nationally Determined Contributions," are also voluntary, which means there is no guarantee that they will be fulfilled. The goal is to limit the increase in the Earth's average temperature to less than 2 degrees Celsius. As moderate as that seems, the global cooperation needed to achieve it remains elusive.

In addition to greenhouse gases' well-established effects on temperatures and sea levels, some scientists believe extreme weather events tied to global warming, including droughts and flooding, will only get worse for future generations without a dramatic reduction in carbon emissions. Experts say stronger steps must be taken to slow the rate of temperature increase. But that's a hard case to make with developing countries that want to accelerate industrialization rather than slow it down.

One such country is India, where millions of people still lack electricity. Indian Prime Minister Narendra Modi sounded a bit indignant last week when he correctly blamed the burning of carbon fuels by industrialized countries for much of the climate change threat. "The lifestyles of a few must not crowd out opportunities for the many still on the first steps of the development ladder," he said.

President Obama was sympathetic. "The United States of America not only recognizes our role in creating this problem; we embrace our responsibility to do something about it," he said. But his remarks were undermined by largely Republican opposition to any global warming pact that Obama might sign, even one that sets modest, voluntary goals to limit the impact on U.S. industry. Their stance is at odds with a New York Times/CBS News poll showing that 63 percent of Americans support an international deal to limit the growth of the greenhouse-gas emissions that cause global warming.

Republicans want Obama to get Senate approval of any agreement. He says that is necessary only for formal treaties and not the pact under consideration. History may one day judge their argument trivial if stronger steps aren't taken to prevent the predicted calamities of climate change.