Global Warming

Decades-Long Weather Shifts Due From Atlantic Cooling

A powerful shift emerging in North Atlantic ocean currents is on the verge of bringing broad-scale changes in the world’s weather that could last for decades, according to a new study.

The Atlantic Multi-decadal Oscillation (AMO) has been found to affect climate for periods of 20 to 30 years. It has been linked to fewer Atlantic hurricanes, drier summers in Britain and Ireland as well as drought in northern Africa’s Sahel region.

The impending onset of the negative (cold) phase of the AMO can be predicted by a slowing of North Atlantic ocean currents, which has recently been observed.

The weaker currents fail to bring warmer waters that typically move from the tropics to the North Atlantic during the positive phase.

Writing in the journal Nature, lead researcher Gerard McCarthy says that since the new negative phase of the AMO could be a degree cooler, it may temporarily offset the effects of global warming in some areas.

The AMO has undergone three major transitions over the past 90 years. It brought significant warming during the 1930s and the mid-1990s, and cooling during the 1970s.

The Global Warming Hiatus Might Not Exist

The global warming hiatus — a decade-plus slowdown in warming — could be chalked up to some buoys, a few extra years of data and a couple buckets of seawater.

That’s the finding of a new study published on Thursday in Science, which uses updated information about how temperature is recorded, particularly at sea, to take a second look at the global average temperature. The findings show a slight but notable increase in that average temperature, putting a dent in the idea that global warming has slowed over the past 15 years, a trend highlighted in the most recent Intergovernmental Panel on Climate Change report.

The term “ global warming hiatus” is a bit of a misnomer. It refers to a period of slower surface warming in the wake of the 1997-98 super El Niño compared to the previous decades. However, make no mistake, the globe’s average temperature has still risen over that period (including record heat in 2014) and temperatures now are the hottest they’ve been since record keeping began in the 1880s. So let’s call it what it really is: a slowdown, not a disappearance of global warming.

The new findings show that even the concept of the slowdown could be overstated.