NOAA recently released its 2018 global temperature summary and the results are in: 2018 was officially the fourth warmest year on record since 1880. The past five years as a whole also rank as the warmest in modern history. Measurements show that the Earth has seen a global temperature increase of about 1.44 degrees F over the last 40 years, and 2 degrees F since 1880 and while that may not seem like much to you — on a global scale it is. A warming climate has consequences across all regions and environments, however, the arctic is warming at a much faster rate than the rest of the world.

The No Nonsense Science

• 2018 was the 4th warmest year on record since 1880, according to 5 major climate organizations
• The arctic has seen an average of 3.5 degrees of warming while the global average is about 2 degrees
• As more dark sea ice is exposed, the dark surface is absorbing more sunlight leading to a further increase in warming known as the albedo feedback
• This results in sea level rise due to the thermal expansion of water from temperature increases as well as the melting Greenland ice sheet
• Increasing ocean temperatures also results in unforeseen effects including a weakening ocean conveyor belt, a shift in storm tracks, and climate changes across varying regions

The arctic has seen approximately 3.5 degrees of warming in the same amount of time as the global average. You might be wondering: “Okay that sounds horrible and all, but why do I care?”. This article will break down the implications that the warming poles have, as well as some of the explanations behind why the arctic warms faster than the mid-latitudes.

What’s the Albedo Feedback?

One of the main and most straightforward reasons the arctic has warmed faster is because of something called the albedo feedback. Albedo is a measurement of the Sun’s energy that is reflected back to space instead of absorbed. Typically, lighter surfaces like clouds and snow covered landscapes reflect more light (scattering all spectrum of light), while dark surfaces such as asphalt or the dark ocean will absorb most of the energy.

This is like when you get caught on on of those humid, full-Sun days where it feels like you’re walking through an actual sauna and you accidentally wore black. You are typically cooler if you wear white clothing as this reflects the Sun’s rays. This analogy can be applied to the warming arctic. As more and more white sea ice melts as a result of global warming, more of the dark ocean surface is exposed, leading to a lower albedo that consequently absorbs more radiation and continues to warm even more.

According to NASA, arctic sea ice extent has been decreasing at a rate of 12.8% per decade relative to a 1981-2010 average as a result of the warming. Below are two images comparing the sea ice extent from 1979 to 2018. A clear decrease in overall coverage can be seen. If you weren’t worried about the poor polar bears and seals before, you definitely should be now!

Research has also noted that a greater warming trend has been seen in the winter versus the summer. Now as you just learned, winter should theoretically have higher albedo from all of the snow and sea ice leading to more reflection and cooler temperatures, so how can this be? This suggests that other factors are at play.

What about the ocean and clouds?

Global warming refers not only to rising air and surface temperatures, but ocean temperatures as well. Water has a higher heat capacity than air does, meaning it takes more energy to heat up your glass of water versus the room around you, for example. This is why ocean temperatures don’t typically become bearable for swimming until the end of the summer, when the sun has had plenty of time to heat it up, but the dark metal on your car becomes hot enough to scorch an egg in a matter of hours. Scientists have observed an estimated .13 degrees F of warming per decade of the oceans since 1910.  As the oceans warm, more water vapor is released into the atmosphere, in turn increasing cloud cover. As mentioned before, this might suggest global cooling since low clouds reflect sunlight. However, research has shown that arctic clouds are not increasing during the summer months, but instead during the fall when the arctic begins entering darkness for the winter (i.e. no sunlight). This means that the clouds are actually acting as a blanket, trapping all of the stored energy and heat from the summer months at the surface, leading to more warming during the winter.

Besides direct sunlight, energy is transported to the poles from the equator through both the ocean currents, and large weather systems. As global warming continues to raise temperatures, the temperature gradient between the equator and the poles decreases, this has shown to shift the jet stream, and consequently storm tracks, northward. The average hurricane can produce energy equivalent to about half the world’s electric producing capacity, or about 10,000 nuclear bombs, all of that energy shifted northward could also be contributing to amplified warming of the arctic and sea ice melting. Both cloud and storm track processes are complicated and difficult to reproduce in climate models, leading to uncertainty in these being a definitive answer to why the arctic is warming at an accelerated rate, however, the basic physics behind these processes are sound and some climate scientists have even said they’d “put their money on it”. Given how stingy we scientists are with our money, I’d take that seriously.

So what are the implications of arctic warming besides sad polar bears?

Besides the dire images we see of the lone polar bear floating away on a small iceberg (which does actually happen by the way), warming polar regions have far more consequences for us as well. For example, the Greenland ice sheet has been melting at a rate greater than in the past three centuries. This has led to an average of about 265 km3 of land ice melted since 1995, which has contributed to an average of .7 mm per year of global sea level rise. This may not seem like much at all, but for those of you who have trouble with math (let’s be honest, that’s most of us), this is about 25% of the yearly total global sea level rise just from Greenland alone.

Again, you’re probably thinking, “That’s not even a millimeter, how does that have effects?”.  The reality is that the .3 mm of global average SLR is just that, an average. It has different effects in different parts of the world. If Greenland continues to melt at current rates through 2050, as much as 20 inches of sea level rise will affect the East coast of the U.S. due to changes in ocean circulation from the melting and runoff. Now THAT would show up on map, covering parts of New York City, Charleston, and countless other coastal cities. I probably wouldn’t be buying up any property on the East coast in the next 50 years if I were you.

This meltwater pouring into the Atlantic ocean from the Greenland ice sheet will also disrupt ocean currents, specifically the Atlantic Meridional Overturning Circulation (AMOC). This is the same current that brings warm, tropical water from the Gulf of Mexico up towards Europe, resulting in a much milder climate than there technically should be (i.e. Ann Arbor, MI and Rome, Italy are at roughly the same latitude, however Rome has a much warmer and arid climate). Recent research has shown that this ocean conveyor belt could be slowing down, causing warmer temperatures to overspread eastern Canada and the Arctic, while colder temperatures begin to overtake Europe. This slowing, diluted current could also affect weather patterns, resulting in sporadic extreme weather events and a northward shifting in the track of Atlantic hurricanes, as mentioned before.

So the next time you question why a few millimeters of sea level rise or a few degrees of temperature increase seems important, remember that averages have different effects across different regions. Also remember that the Arctic warming faster than the rest of the world has consequences for us all, and although the climate, atmospheric, and ocean system interactions are incredibly complicated and hard to replicate in models, the basic science is there. As we continue to warm at this rate through the middle of the century, we may begin to see unforeseen consequences not just in the arctic, but everywhere.