Opinion » Eco Logic

Climate by the numbers

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Scientific inquiry can be viewed as a form of slow-motion, hyper-exacting debate that turns on the rejection of hypothesized explanations for particular observations, allowing for an incrementally honing-in on a most likely scenario. As such, scientists test and refine each other's theories, on which they rarely concur at the outset. The process thus usually leads to some kind of consensus or basic understanding, a point from which everyone can work to learn more.

This has certainly been the case when it comes to climate change—arguably the single most researched topic in the history of the world. Which is why continued denialism around the subject—either of the individual or institutional form—is so laughably absurd. Tens of thousands of studies in respected, peer-reviewed journals are in almost unanimous agreement on key basic facts. Let's start with the most obvious, temperature, and move on from there.

Average global temperature increased 0.85 C between 1880 and 2017, a full 0.6 C in the past three decades alone. Based on both NASA and National Oceanic and Atmospheric Administration (NOAA) data, the 2017 average global temperature itself was 0.84 C above the 20th-century average of 13.9 C, making it the third-warmest year on record behind 2016 (warmest) and 2015 (second warmest); since 2000, that record has been broken five times, while global temperature hasn't dipped below the average since 1976. To put that in perspective, over the period 1900 to 1980 a new temperature record was set on average every 13.5 years; since then, the rate has increased to every three years.

Now let's talk about the cryosphere (a blanket term for the snowy and icy areas of the planet). Over the past half century, alpine and polar ice have been disappearing at unprecedented rates. Ditto for permafrost, in which the seasonal active layer is becoming thicker, the lower permanent layer warmer, and surface permafrost structures lost—all contributing to an increase in microbial and chemical action that releases greenhouse gases like carbon dioxide, methane and nitrous oxide. This global "thaw" is aided by a rise in average sea level, warmer oceans, increased snow insulation in some areas, and in others, thinning snow cover that normally reflects sunlight back into the atmosphere.

The upshot is a positive feedback loop of melting and warming and increasingly extreme weather, including wildfires and hyper-destructive tropical storms. Related effects include precipitous global declines in the thickness and extent of glaciers: a 2014 study cited B.C.'s 17,000 glaciers as receding "at an alarming rate." Polar areas like the Canadian Arctic are warming over twice as fast as the rest of the planet (a full 3.0 C in 30 years), and end-date snow cover in Canada's north now averages three weeks earlier than in 1950. The most sensitive barometer of change, however, may be the extent of polar sea ice.

Northern hemisphere sea-ice shrinkage has outpaced all models: levels predicted for 2025 were achieved in 2007, and the past four years have seen the lowest sea ice cover ever recorded: 2015, 2016, 2018 and 2017. Total volume of Arctic ice has diminished by over half since 2004 and milder winters ensure that any ice that does form is less substantive—average thickness of sea ice has decreased 30–50 per cent globally. In summer 2013, spring breakup in the Arctic began 57 days earlier than average, and each of the past two winters have seen unprecedented mid-winter Arctic heatwaves.

Early millennium models predicted a seasonally ice-free Arctic between 2050 and 2100, but as early as 2011 we were on a trajectory to see this within a decade based on measurements showing more rapid response in the Arctic to atmospheric CO2 than expected.

In the Southern Hemisphere, scientists reported in May 2014 that the breakup of the 2.2 million km3 western Antarctic ice sheet had begun and was now irreversible; they have been proved correct each year since. Ice loss may merely be a concerning phenomenon, but "irreversible" is as frightening as it sounds.

Against this backdrop, the current warming trend will be neither staid nor reversed—let alone addressed in our lifetimes. By all measures we're on an inexorable path to widespread drought, more powerful storms, rising and warming oceans, and an ice-free Arctic. Isn't it time the deniers started accepting what we all know to be true, so we can get on with adapting to the current scenario and making sure we don't make it worse?

Leslie Anthony is a science/environment writer and author who holds a doctorate in connecting the dots.

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