Update April 10, 2019 March AMO Results now available and included in Decadal graph below.
For the last few years, observers have been speculating about when the North Atlantic will start the next phase shift from warm to cold. Given the way 2018 went, this may be the onset. First some background.
An example is this report in May 2015 The Atlantic is entering a cool phase that will change the world’s weather by Gerald McCarthy and Evan Haigh of the RAPID Atlantic monitoring project. Excerpts in italics with my bolds.
This is known as the Atlantic Multidecadal Oscillation (AMO), and the transition between its positive and negative phases can be very rapid. For example, Atlantic temperatures declined by 0.1ºC per decade from the 1940s to the 1970s. By comparison, global surface warming is estimated at 0.5ºC per century – a rate twice as slow.
In many parts of the world, the AMO has been linked with decade-long temperature and rainfall trends. Certainly – and perhaps obviously – the mean temperature of islands downwind of the Atlantic such as Britain and Ireland show almost exactly the same temperature fluctuations as the AMO.
Atlantic oscillations are associated with the frequency of hurricanes and droughts. When the AMO is in the warm phase, there are more hurricanes in the Atlantic and droughts in the US Midwest tend to be more frequent and prolonged. In the Pacific Northwest, a positive AMO leads to more rainfall.
A negative AMO (cooler ocean) is associated with reduced rainfall in the vulnerable Sahel region of Africa. The prolonged negative AMO was associated with the infamous Ethiopian famine in the mid-1980s. In the UK it tends to mean reduced summer rainfall – the mythical “barbeque summer”.Our results show that ocean circulation responds to the first mode of Atlantic atmospheric forcing, the North Atlantic Oscillation, through circulation changes between the subtropical and subpolar gyres – the intergyre region. This a major influence on the wind patterns and the heat transferred between the atmosphere and ocean.
The observations that we do have of the Atlantic overturning circulation over the past ten years show that it is declining. As a result, we expect the AMO is moving to a negative (colder surface waters) phase. This is consistent with observations of temperature in the North Atlantic.
Cold “blobs” in North Atlantic have been reported, but they are usually winter phenomena. For example in April 2016, the sst anomalies looked like this
But by September, the picture changed to this
And we know from Kaplan AMO dataset, that 2016 summer SSTs were right up there with 1998 and 2010 as the highest recorded.
As the graph above suggests, this body of water is also important for tropical cyclones, since warmer water provides more energy. But those are annual averages, and I am interested in the summer pulses of warm water into the Arctic. As I have noted in my monthly HadSST3 reports, most summers since 2003 there have been warm pulses in the north atlantic.
The AMO Index is from from Kaplan SST v2, the unaltered and not detrended dataset. By definition, the data are monthly average SSTs interpolated to a 5×5 grid over the North Atlantic basically 0 to 70N. The graph shows the warmest month August beginning to rise after 1993 up to 1998, with a series of matching years since. December 2016 set a record at 20.6C, but note the plunge down to 20.2C for December 2018, matching 2011 as the coldest years since 2000. Because McCarthy refers to hints of cooling to come in the N. Atlantic, let’s take a closer look at some AMO years in the last 2 decades.
This graph shows monthly AMO temps for some important years. The Peak years were 1998, 2010 and 2016, with the latter emphasized as the most recent. The other years show lesser warming, with 2007 emphasized as the coolest in the last 20 years. Note the red 2018 line is at the bottom of all these tracks. The short black line shows that 2019 began slightly cooler than January 2018 The February average AMO matched the low SST of the previous year, 0.14C lower than the peak year February 2017. March 2019 is also slightly lower than 2018 and 0.06C lower than peak year March 2016.
With all the talk of AMOC slowing down and a phase shift in the North Atlantic, it seems the annual average for 2018 confirms that cooling has set in. Through December the momentum is certainly heading downward, despite the band of warming ocean that gave rise to European heat waves last summer.
Comment to be removed.
It is one phenomenon, two phenomina.
But thank you for the post.
Reblogged this on Climate Collections.
The North Atlantic cold blob developed in some of the warmest years of Atmospheric and Oceanic temperature record keeping. This freshing of the North Atlantic ( cold fresh water stratification at the surface ) has (in part) slowed the Atlantic Meridional Overturning Circulation and I find this to be worrisome. My concern about the North Atlantic Cold Blob is the potential association with the past couple of decades involving the anticyclonic spin of the Beaufort Gyre. Prior to progressive loss of Arctic Sea Ice Extent, the Beaufort Gyre was observed to reverse its spin and dump a (controlled amount) of frigid fresh water into the North Atlantic Ocean. The current volume of cold fresh water in the Beaufort Gyre, I believe, is equivalent to “All” the fresh water contained in the Great Lakes. At some point in time, I suspect we may observe a breach of the perimeter’s salt water containment (without a reversal of the anticyclonic spin), and the Beaufort Gyre will dump an unstoppable amount of cold fresh water into the North Atlantic and mess up the Salinity Equation that allows the normally warm salt water of the North Atlantic to cool off & sink, propelling the Great Oceanic Conveyor south along the deep ocean. If this comes about, we may observe sea surface water temperatures in the (stagnant areas) of our Tropics heating up…which will add to the fueling potential of hurricanes along with Abrupt Intensification of Storms. Ireland, Scotland, England, the west coast of France, eastern Canada and northeastern United States will likely cool down in summer. Small nudges in global climate change may produce large swings in severe weather events revealing the most vulnerable. Civil society is unlikely to continue on as “Business As Usual” without acknowledging, understanding and appreciating the science behind global climate change. According to the Oxford Martin School, Oxford, England’s “Our World in Data,” there is about 50 years of known gas and oil reserves left. We are in a race between consumption and depletion. I believe we should leave 90% of the known oil and gas reserves in the ground and deal with the transgenerational mess we have already created. Unfortunately, a Hegemony Style fossil fuel energy business has replaced DEMOCRACY in America, so mitigation and adaptation are not on the back burner, they are not even on the table. Indecorous should come to mind. Think about it, please. Encourage those in government that the climate change challenge will not be addressed appropriately by small dose(s) of INCREMENTALISM, i.e., “baby steps” towards transitioning to Renewable Energy Sources. Sorry if there’s any spelling or grammatical errors, not proofread. T
Thanks for commenting Doug. Your scenario is well presented. I don’t agree with it, however. IMO the next decades are more likely to be cooler than warmer, and we shall need reliable, affordable energy as well as robust infrastructure for the more extreme weather that accompanies cold periods. Renewables are a dead end and we should invest in realistic sources of energy, nuclear for example, and a major emphasis to see if fusion is possible and scalable. As for your peak oil projection, it has been rendered passe by today’s extraction technologies with further advances to come.
Okay, so I am on the upslope of the global climate change learning curve, having recently retired I admit that nearly all my energies were previously focused on identification and treatment strategies involving autoimmune diseases. But, having reviewed the Insideclimate News Series, “Exxon: The Road Not Taken,” September 16, 2015, September 17, 2015, September 22, 2015, October 8, 2015, October 22, 2015, November 25, 2015, December 1, 2015 and December 22, 2015 data….I find it incomprehensible that Exxon Energy Company and the fossil fuel-friendly Trump Adminstration have not been taken to court for Crimes against Humanity. Back in the late 1970’s and early 1980’s, Exxon’s own global climate change research scientists were all well aware of the path towards a (nearly) uninhabitable earth. Yes, in the name of profit…chasing after the almighty dollar. This is speculation on my part, but I believe that perhaps Exxon decision makers were under the delusion that they would be the only surviving “remnant” on an acquired earth environment that no one in their right mind would want to live in. We are all in for a rough ride. Nearly all of “Sir Tweets a lot’s” communications have been indecorous.
Doug, thanks for commenting. I think you have some assumptions that don’t bear up under scrutiny. On global warming/climate change there is a lot of disinformation out there, as well as hidden facts to be uncovered. If you are brave enough to reconsider your premises, live the “examined life” as Plato admonished, your views can shift from opinions to knowledge.
Start with https://rclutz.wordpress.com/2019/02/06/2019-update-climate-reductionism/
See also https://rclutz.wordpress.com/2018/01/11/rise-and-fall-of-cagw/