The Financial Times reports:
A range of factors have been pinpointed for what has come to be called the “hiatus” or “pause” in warming, which the scientists said they expected to be temporary.
These include small airborne particles known as aerosols from volcanic eruptions that have a cooling effect as they reflect sunlight back into space; the impact of the regular cycle of solar activity; the sensitivity of the climate to greenhouse gases, and the way the oceans absorb heat.
“We don’t fully understand the relative importance of these different factors,” Professor Rowan Sutton of the University of Reading said at a briefing with Met Office scientists in London. [Emphasis added]