Climate change can give rise to abrupt and unexpected outcomes in the Earth system. Last week, a new article in Nature Scientific Reports claimed that a collapse of the Atlantic Meridional Overturning Circulation (AMOC) could lead to a rapid cooling in the Northern Hemisphere, and that this cooling in turn could obliterate global warming for a period of 15-20 years. Only to revert to a warming pattern some 40 years later.

According to professor Sybren Drijfhout, his model showed that “The planet earth recovers from the AMOC collapse in about 40 years when global warming continues at present-day rates, but near the eastern boundary of the North Atlantic (including the British Isles) it takes more than a century before temperature is back to normal”.

What is so scary about this study is that the effect of atmospheric cooling due to an AMOC collapse is associated with heat flow from the atmosphere into the oceans, which has actually occurred during the last 15 years. A well known fact to many scientists but somewhat unclear to the public which has been bombarded with climate deniers "warming hiatus" nonsense.

According to Drijfhout, when there is a net cooling effect heat flows from the oceans to the atmosphere but when there is net warming effect then this energy flow is reversed. In other words, the world’s oceans have acted as giant heat sinks, counteracting the greenhouse effect in regards to atmospheric temperatures, for the last decade. But this period is now over, according to Drijfhout. The oceans are again releasing heat, amongst others due to shifting ocean and wind patterns and a strong El Niño.

Every 3-7 years variations in tropical winds and pressure shift warm ocean water east to the South American coast, causing an El Niño event. Last time we experienced a really strong El Niño was in 1997/1998 but this years event have the potential to top that record, according to many scientists. There is a 90% chance that El Niño will continue through the Northern Hemisphere winter 2015-16 (NOAA, 2015).

This week average temperatures jumped to above 1.9C which is much sooner than most models predicted, that indicated it would occur by October/November. We could reach ocean warming of 2.2 or even 3C above average by the end of the year. Such temperature anomalies would exceed the maximum values seen during the record 1997/98 event.

Combining our current climate forcing with such a powerful El Niño could mean that global average atmospheric temperatures will continue to hit record highs. The heat coming from the Pacific Ocean is massive and will probably reinforce the the "hot blob" in the Northern Pacific as well as transport warmer waters into the Arctic, through the Bering Strait. This could increase the melting of Arctic sea ice with a reinforcing feedback of further warming in the region. A powerful El Niño could also increase storminess along the south and eastern US and across the North Atlantic where a cold pool south of Greenland (associated with a weakening North Atlantic current) is already intensifying storms.

The risk of abrupt and/or irreversible climate change is determined by a crossing of tipping elements in the Earth system. One such tipping element is the North-South ocean current circulation in the Atlantic Ocean, also known as the Gulf Stream system. The Gulf Stream system is one of Earth’s most important heat transport systems, pumping warm water northwards and cold water southwards. It is responsible for the mild climate in northwestern Europe and the most important source of heat transport to Scandinavia.

A potential abrupt change, or slowing down of the Gulf Stream circulation could lead to a weakening of heat transportation towards the Arctic which in turn would result in a cooling effect of high northern latitudes (including Scandinavia). 

Scientists at Potsdam University have now found evidence for a slowdown of the Gulf Stream (published in Nature). Multiple lines of observation suggest that in recent decades the current system has been weaker than ever before in the last 1000 years. The gradual but accelerating melting of the Greenland ice-sheet, caused by man-made global warming, is a possible major contributor to the slowdown.

The blue cooling spot south of Greenland: NASA GISS warming map 1901-2013. Source: PIK-Potsdam

“Now freshwater coming off the melting Greenland ice sheet is likely disturbing the circulation”, says Jason Box of the Geological Survey of Denmark and Greenland. The melting glaciers are diluting the North Atlantic ocean salty water. Less salty water is less dense and doesn’t sink to the ocean deep as easy. 

The observed cooling in the North Atlantic, just south of Greenland, is stronger than what most climate models have predicted so far. One reason for this is that most computer simulations underestimate the stability of the Gulf Stream or don’t account properly for the Greenland ice sheet melt. This is yet another example where observations suggest that climate models are too conservative when it comes to the pace at which certain aspects of climate change are proceeding.

A slowing down of the Gulf Stream will not lead to a new ice age but it could have major negative effects on ocean ecosystems and thereby fisheries and coastal livelihoods. A slowdown also adds to the regional sea-level rise affecting cities like New York and Boston. Further weakening of the current could also result in temperature changes in the northern latitudes, influencing weather systems on both sides of the Atlantic, in North America as well as Europe.

Plastic materials is any of a wide range of synthetic compounds that are malleable. Plastics often contain many chemical substances and are commonly derived from petrochemicals, but some are partially natural. It takes about 2 kg oil for every 1 kg plastic production, from a life-cycle perspective. The more advanced plastics requires more energy for production. Due to their relatively low cost, ease of manufacture, versatility and imperviousness to water plastics are used in an enormous and expanding range of products from food packaging to computers and cars. Motivated by the finiteness of oil and threat of climate change, bioplastics are being developed from cellulose and starch. Most plastics, however, are durable and degrade very slowly, some taking centuries. Plastic pollution pose as a major problem for the world's marine life and food web. 

Humans have little consideration for how much waste we continuously dump into the world's oceans and its effects on marine life. Plastic pollution is nowadays common throughout the marine environment. In a new study in PLOS, scientists from the US, France, Chile, Australia and New Zealand report for the first time an estimated number of 5 trillion pieces of plastic in total afloat at sea. With a collective weight of over 250 000 tonnes, it weighs more than the entire biomass of humans (Guardian, 2014). The volume of plastic pieces, largely derived from products such as food and drink packaging and clothing was calculated from data collected in 24 expeditions during 2007-2013 across five sub-tropical gyres.

Large pieces of plastic can strangle animals such as seals, while smaller pieces are ingested by fish and then fed up the food chain, all the way to us humans. Chemicals contained within plastics and the pollutants they attract once they’re in the marine environment are toxic and can cause great harm to animals and humans. It’s hard to tell how much pollution is being ingested by marine life but plastics definitely contribute to increased toxins along the food web. While spread out around the globe, much of the plastic accumulates in five large ocean gyres, which are circular currents that churn up plastics in a set area. The gyres contribute to the problem because they shred the plastic before dispersing it. This micro-plastic continue to disperse and interact with entire ocean ecosystems (see figure 1 and 2).

Researchers predict the volume of plastic pollution will increase due to rising production of throwaway plastic, with only 5% of the world’s plastic currently recycled. Policymakers need to understand the scale of the problem and take action accordingly. Some countries have taken measures to restrict plastic pollution. Germany has changed policy so that manufacturers are responsible for the waste they produce. By putting more responsibility on producers a larger shift towards recycling in possible. Recycling plastic can save energy and reduce carbon pollution but a major hindrance is how to sort plastics effectively since its made up out of so many different chemical compounds (polymers). 700 000 tonnes plastic is thrown away unsorted in the Nordic countries every year. Three new reports (2014) from the Nordic Council of Ministers describe methods for improving collection, sorting, and recycling of plastic waste in the Nordic countries. “Collection and recycling of plastic waste” presents the first steps towards improved nordic systems for collection and recycling. Every year 65 000 tonnes of plastic is burned at recycling stations.“Guideline for plastic sorting at recycling centres” looks at municipal recycling station practices for increasing collection of plastic materials of higher quality. Despite usable recycling techniques being available, less than 30% of plastic waste is recycled. “Plastic value chains - Case WEEE” identifies a substantial potential for increased recycling of plastics from electronic waste. This field is an excellent case where circular economy principles could be applied, the potential for improvements being large.