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Shawn Vestal: The consensus on warming and human activity is ‘unequivocal’

If you’re a regular reader of this page, then you’ll understand that a review of the actual, undistorted climate science, and the role of human beings in warming the planet, is in order.

Here goes.

It’s getting warmer and human activity is the primary cause: It should go without saying at this late stage in the emergency, but this is not the claim of one or two or 10 or 50 left-wing politicians.

It’s a warning from the vast majority of scientists who study the subject all over the world.

“Since systematic scientific assessments began in the 1970s, the influence of human activity on the warming of the climate system has evolved from theory to established fact,” is the way NASA puts it.

The International Panel on Climate Change, a global review of all climate science conducted by thousands of scientists, repeatedly used the term “unequivocal” to describe the strength of the scientific knowledge about the human influence on the climate.

“Human activities, principally through emissions of greenhouse gases, have unequivocally, caused global warming, with global surface temperature reaching 1.1°C above 1850-1900 in 2011-2020,” the most recent IPCC report, issued in March, concluded.

Survey after survey shows that nearly all the world’s climate scientists agree with this. Four separate studies since 2016 show that 97%, 99%, more than 99% and 100%, respectively, of climate scientists were in agreement about this basic fact.

Greenhouse gases are the culprit: Atmospheric concentrations of carbon and methane are at all-time highs, and they have gotten worse in recent years even as the warnings have grown more dire. Emissions were estimated to be 12% higher in 2019 than in 2010 and 54% higher than in 1990. We have known the truth about global warming during all of that period, and failed to act, in large part due to factual charlatanism and political failures.

The consequences, if left unchecked, are dire: It’s alarming – but not alarmist – to note that we are already seeing the effects of global warming, which will grow even worse if unchecked by dramatic reductions in greenhouse gases.

Heat waves and droughts are increasing. Spring snow cover is shrinking. Glaciers are retreating. The oceans are warming, rising and acidifying. The number of annual extreme weather events – record highs, once-in-a-century weather events – is growing. Wildfires are worsening. Coastal areas face particular challenges.

The IPCC said that more than 3 billion people around the planet are “highly vulnerable” to climate change, exposed to threats to food and water access, deadly extreme weather, and damage to coastal infrastructure. This includes communities in Africa, Asia, Central and South American, and small islands. Between 2010 and 2020, the IPCC reports, human mortality from floods, droughts and storms was 15 times higher in these highly vulnerable regions than in other places.

Warming is contributing to more wildfires: The number of large fires burning in the Western U.S. has grown dramatically since 1984, and there is evidence that global warming is a big reason. While it’s true that there are many factors involved, including the amount of vegetation and forest management practices, researchers in 2016 concluded that the effects of global warming – increased drier vegetation and reduced snowpack, etc. – caused more than half the increases in “fuel aridity” since the 1970s and doubled the amount of land considered a “forest fire area” since 1984. There is also strong evidence that fires are getting bigger and burning longer – effects that are also associated with climate change.

The effects in our region are already widespread: The annual average temperature has risen almost 2 degrees since 1900 in Idaho, Oregon and Washington, according to the USDA’s Northwest Climate Hub. (Alaska’s annual temperature has risen more than anywhere else, increasing by 3 degrees since 1925).

Precipitation trends are changing, with a reduction in summer rain and more winter precipitation falling as rain, rather than snow. Snowpacks are smaller, overall, and they melt earlier in the spring. Droughts are more common and expected to increase. More warming is expected to worsen these consequences.

The “hockey stick” is accurate: People trying to stupidify the public like to claim that the so-called hockey stick graphic – which shows the historical trend in global temperatures as a “handle” of relative stability for centuries followed by a rising “blade” of temperature increases in the late 20th century – has been “discredited.”

That is flatly wrong. The hockey stick is roughly as discredited as the results of the 2020 election – in other words, not at all discredited, except among those who consume a junk-fact diet. The basic pattern of the temperature rise has been confirmed more than a dozen times, according to Scientific American.

Robin Lamboll, a British climate scientist, put it this way: “The different ways to estimate historic climates have become more numerous, but all with broadly the same message, and so the conclusions of the original graph have become only more solid since 1999.”

Significant change is required: Some consequences are inevitable at this point, but the worst effects of warming can be offset by “deep, rapid, and sustained global greenhouse gas emissions reduction,” the IPCC said.

The best estimates now predict that warming will likely exceed 1.5 degrees Celsius in this century – avoiding the 2-degree rise seen as urgent to avoid the worst consequences. It is far from certain that the world is taking the steps to avoid that. Deep cuts in emissions could result in a “discernable slowdown” in warming within 20 years. What it will take, the IPCC said, is “net zero CO2 emissions” – meaning an elimination of carbon emissions or a balance between carbon emitted into the atmosphere and carbon removed.

Is there the political will and widespread scientific understanding to make this happen? In a paper published last year in the journal Nature, scientists estimated that there was a slightly higher than 50% chance that the we can avoid a 2-degree rise in temperatures this century – if all the pledges countries made under the Paris Agreement are kept.

Which is a big if.

It’s past time to ignore the doubt merchants and act: “The choices and actions implemented in this decade will have impacts now and for thousands of years,” the IPCC concluded.

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