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Climate Change is still hotly (!) debated in some quarters, but at least science has an answer about Oregon's climate

COURTESY NOAA - This graph charts Oregons summer high temperatures, starting with 1895, and continuing up through this past August. Despite lots of variations, year by year, the overall trend is clearly upward.The Southeast Portland Rotary Club, of which your editor is a longtime member, had the same question most residents here had after our 116 degree temperature reading on June 28: Is our climate really changing, or are we just having occasional drastic exceptions to the norm? And if it really is changing, what is causing it? The club sought a local meteorologist to discuss it, and those consulted pointed to a nationally-recognized expert on the topic at Oregon State University in Corvallis: Dr. Philip Mote, Vice Provost and Dean of the Graduate School at OSU, and active in the Oregon Climate Change Research Institute (OCCRI) and the NOAA-funded Climate Impacts Research Consortium (CIRC) for the Northwest. He agreed to address the club via ZOOM on Monday, October 11, at noon.

COURTESY OF DR. PHILLIP MOTE, OSU - These four graphs show long-term trends for four different variables in causing Oregons climate: The ENSO sea surface temperature at the equator; the periodic volcanic eruptions that can emit aerosols that temporarily cool the Earth; the output of the sun, which does vary over time; and the level of manmade Greenhouse Gases in our air.Dr. Mote proved an engaging speaker, and he brought with him a variety of graphs to make absolutely clear what is going on with our weather – and why until recently did it not seem to be changing rapidly. One graph he presented, reproduced here, was courtesy of the National Weather Service, and it showed the temperature trend of the last twelve decades of summers (June through August) here in Oregon. On that graph, the "mean" temperature of the whole period – all the monthly high temperatures averaged over the entire time period – was a horizontal line down the middle. Overlaid on that line was a second line showing the annual summer average temperature trend across those 120 years, averaging the annual temperatures of each month of each year: It starts below that horizontal line in 1895, and continues through this August, in 2021, rising to its highest point. The annual monthly maximum temperatures vary, and make a climbing series of jagged up-and-down tracks, but the trend is clearly warmer. So, in Oregon, there has been a steady trend of warming. How do we know what is causing it? And how can we know whether it is just long-term weather variations, or whether it is real and will continue? There was a graph for that, too. In fact, four graphs on one slide! Starting in 1900 and continuing through 2020, three of the graphs showed little substantial change over the entire period. These were the ENSO trend, which measures the equatorial sea surface temperatures that influence our weather; it was pretty level, with some recent spikes, but currently actually cooler than average. The "Volcanoes" chart showed how volcanic activity around the world periodically threw aerosols into the atmosphere that could cool the Earth down temporarily. The third chart, "Solar Irradiance", measured how much energy from the sun we received over the years – the sun does vary in its output over the years; there is a mild uptrend over this period of time, but relatively little variation, in output percentage terms. COURTESY OF DR. PHILLIP MOTE, OSU - Drawn from a published report, Working Group: Contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, co-authored by a large number of scientists from countries around the world, heres the worldwide temperature trend - for the last two millennia on the left; and for the 1850-2020 period on the right. And then there is the fourth chart – which measures "Anthropogenic GHGs" in our Oregon air: That is, man-made "Greenhouse Gases". This chart answered both of the club's questions: These gases were rising here slightly from 1900 to 1940, then dipped slightly for a few years, and then – starting around 1965 – started climbing sharply, right up to the current day. Consequently, through the 1960s and probably even the 1970s, it didn't seem to most of us as if there were any major effects taking place on the Oregon climate, leading some to think that Oregon was escaping "global warming" that was reported elsewhere. But, since then, we have been experiencing our own definite warming trend, and it continues today, attributable mostly to manmade "Greenhouse Gases". Those include carbon dioxide, methane, hydrocarbons, other industrial gases, as well as whatever emerges from our auto exhaust pipes. Dr, Mote, having demonstrated the local climate trend in Oregon, concluded with a graph showing the worldwide temperature trends of the last 2,020 years (to provide a little perspective!) – side-by-side with a graph of the global temperature trend from 1850 to the present day (showing the projected temperature trend without human emissions superimposed over the trend with human emissions included).

The very recent sharp rise is particularly striking – especially on the 2,020-year graph, much of which is derived from geological findings of temperature over these two millennia. It appears that it hasn't been as hot on Earth as it is right now since the time of the dinosaurs, 100,000 years ago! (There is a temperature range to the left of the first chart, showing that.)

So, the facts do seem to speak for themselves, as Dr. Mote suggested. As to what to do about this – that's another topic, and is currently the subject of worldwide debate. But at least the answer sought with the Rotary Club's two questions, concerning Oregon, seems clear – things are indeed really getting warmer here, and it's mostly due to the recent rise in "Greenhouse Gases".


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