When Canadian soldiers pulled out of Flanders in November 1917, they left one of the most notorious First World War battlefields.
The Third Battle of Ypres — you know to expect the worst when battles, wars, movies are numbered — had begun that July. Meant to divert German forces from the French army fighting to the south, the campaign was also supposed to capture towns on the Belgian coast.
Among the first battle objectives, however, was a small farming village. The ruins of Passchendaele rested on the last of several ridges to the east and south of Ypres that had been held by German troops since 1914. Although rising only a few dozen metres above the plain, the ridges offered unobstructed views — and target practice — right to Ypres itself.
By the time the Canadians were called in that October, the plain was a waterlogged, shell hole-pitted morass; hundreds of thousands of soldiers had been wounded or died; Passchendaele was nothing but pulverized brick and dust; and the battle lines had barely moved in weeks.
Much of Flanders is low-lying, former marshland. By 1917, near-constant shelling over three years of war had destroyed the network of canals and ditches that drained the area.
Nonetheless, the ground should have been passable. Weather records showed August in Flanders was typically sunny, dry and breezy.
But that August, heavy rains drenched the region regularly. The water drained down from the surrounding ridges and collected on the plain.
Soldiers slogged through the resulting mud up to their knees. Shell holes became deep, steep-, slippery-sided sloughs. Stepping off any of the timber trackways laid over the mud could mean drowning in the sludge.
The mud made moving field guns into position difficult. It made firing accurately exceedingly challenging — recoil tipped the guns backward into the mud, with shots going high, wide or both … even landing among comrades farther up the line.
Some historians have since suggested the battle itself might have caused the weather that bogged the fighting. The bombardments, exploding mines and constant shelling heaved tonnes of dirt, dust, chemicals and other particles into the air. Those high-flying particles and aerosols might have shifted local weather.
Weather records for the area show August as predominantly dry for decades, until 1917 and 1918 — two years of heavy local shelling — when hot and dry suddenly turned to cool and soggy. The records then show consistently hot and dry August weather for subsequent years, until fighting and bombing began again in the region, during the Second World War, 25 years later. As soon as that ended, normal weather patterns reasserted themselves.
We, too, have experienced the way drifting smoke can affect weather. In early September, wildfire smoke from the B.C. Interior filtered the sun here in Victoria. With less solar radiation getting through, temperatures forecast to reach the high 20s and low 30s stayed in the low 20s.
We also now know that wildfire (and carpet bombing) creates its own weather. The heat causes novel wind patterns that affect airflow in the surrounding region. Wildfire and volcanic eruptions can also cause massive thunderheads that can produce lightning storms with or without rain.
Volcanic eruptions have a longer reach. They shoot soot, ash and aerosols high into the atmosphere. After Mount Pinatubo blew in 1991, global temperatures fell by about two degrees on average for the next two years. High latitudes and altitudes experienced longer, colder, snowier winters, and it rained more, too. Glacier ice cores show similar temperature dips and snow accumulation after other massive volcanic eruptions known to have taken place in past centuries.
Sometimes we deliberately spray chemicals into the air from airplanes to modify weather. Cloud-seeding adds micro-particles to the lower atmosphere. The particles attract water droplets, causing droplets to become raindrops or ice pellets. Most cloud-seeding proponents hope to encourage rainfall, but the Alberta government ran a cloud-seeding program for many years to try to reduce the destructiveness of prairie hailstorms, and some airports practise it to reduce local fog.
Whether war caused the weather that added to the horror that was the Battle of Passchendaele, smoke, dust and other atmospheric pollution have long-reaching effects.
And the shadow of those effects can affect events today that become history tomorrow.
