geografia: Year Without a Summer

Evidence: 100 • authority: 72

The year 1816 is known as the Year Without a Summer because of severe climate abnormalities that caused average global temperatures to decrease by 0.4–0.7 °C (0.7–1 °F). Summer temperatures in Europe that year were the coldest of any on record between 1766 and 2000, resulting in crop failures and major food shortages across the Northern Hemisphere. Evidence suggests that the anomaly was predominantly a volcanic winter event caused by the massive eruption of Mount Tambora in the Dutch East Indies (modern-day Indonesia) in April 1815. This eruption was the largest in at least 1,300 years (after the hypothesized eruption causing the volcanic winter of 536); its effect on the climate may have b…

Evidence: 44 • authority: 72

A volcanic winter is a reduction in global temperatures caused by droplets of sulfuric acid obscuring the Sun and raising Earth's albedo (increasing the reflection of solar radiation) after a large, sulfur-rich, particularly explosive volcanic eruption. Climate effects are primarily dependent upon the amount of injection of SO2 and H2S into the stratosphere where they react with OH and H2O to form H2SO4 on a timescale of a week, and the resulting H2SO4 aerosols produce the dominant radiative effect. Volcanic stratospheric aerosols cool the surface by reflecting solar radiation and warm the stratosphere by absorbing terrestrial radiation for several years. Moreover, the cooling trend can be…

Evidence: 44 • authority: 72

The volcanic winter of 536 was among the most severe and protracted episodes of climatic cooling in the Northern Hemisphere in the last two thousand years. The volcanic winter was caused by at least three eruptions of uncertain origin, with several possible locations proposed in various continents. In early AD 536 (or possibly late 535), an eruption ejected great amounts of sulfate aerosols into the atmosphere, reducing the solar radiation reaching the Earth's surface and cooling the atmosphere for several years. In March 536, Constantinople began experiencing darkened skies and lower temperatures. Summer temperatures in 536 fell by as much as 2.5 °C (4.5 °F) below European normal. The ling…

Evidence: 37 • authority: 72

Year 536 (DXXXVI) was a leap year starting on Tuesday of the Julian calendar. At the time, it was known in the Roman Empire as the Year after the Consulship of Belisarius. In 2018, medieval scholar Michael McCormick nominated this year as "the worst year to be alive" because of the volcanic winter of 536 caused by a volcanic eruption early in the year, causing average temperatures in Europe and China to decline and resulting in crop failures and famine for well over a year.

Evidence: 31 • authority: 69

But the main contributor to the unusually cold year was the volcanic winter caused by the eruption of Mount Tambora, located on the island of Sumbawa, Indonesia. In April of 1815, it erupted in what was one of the two largest eruptions in the past 2000 years, and the largest eruption in recorded history. This eruption had a Volcanic Explosivity Index (VEI) of 7, which is a supercolossal event. The highest VEI number ever assigned has been an 8, a mega-colossal event — an example is the Yellowstone eruption in 640,000 BC. For point of reference, the eruption of Mount St. Helens ranks a 5 on the logarithmic scale. The explosion of Mount Tambora was heard up to 1,600 miles away. Ash fell over 800 miles away. The volcanic eruption has been blamed for up to 71,000 deaths. Besides the famine caused by the temporary climate change, the volcanic eruption is also blamed for the severity of the typhus epidemic in Europe and the Mediterranean in the years immediately following; and for a new strain of cholera that broke out in India because the normal monsoon season was disrupted. The amount of volcanic ash spewed into the atmosphere by Mount Tambora lowered global temperatures by as much as 0.7—1.3 °F. Much cooler temperatures in many parts of the world the year after the eruption led to worldwide harvest failures, which is why that year is also known as the "Poverty Year."

Evidence: 25 • authority: 72

There are numerous effects of climate change on agriculture, many of which are making it harder for agricultural activities to provide global food security. Recent research has found that climate change is likely to exacerbate the existing environmental impacts of agriculture by lowering crop productivity, reducing the effectiveness of agrochemicals, increasing soil erosion and pest pressures, and thereby driving greater use of land, water and inputs. Rising temperatures and changing weather patterns often result in lower crop yields due to water scarcity caused by drought, heat waves and flooding. These effects of climate change can also increase the risk of several regions suffering simul…

Evidence: 25 • authority: 72

Present-day climate change includes both global warming—the ongoing increase in global average temperature—and its wider effects on Earth's climate system. In a broader sense, climate change also includes previous long-term changes to Earth's climate. The modern-day rise in global temperatures is driven by human activities, especially fossil fuel (coal, oil and natural gas) burning since the Industrial Revolution. Fossil fuel use, deforestation, and some agricultural and industrial practices release greenhouse gases. These gases absorb some of the heat that the Earth radiates after it warms from sunlight, warming the lower atmosphere. Earth's atmosphere now has roughly 50% more carbon dioxi…

Evidence: 0 • authority: 91

Evidence: 0 • authority: 91