Here Comes Fred

As expected, Tropical Storm Six has become Tropical Storm Fred, and its current trajectory has it heading in the direction of Atlanta.  If it passes, it will be the third hurricane this year to reach this relatively inland city.  The increase in the frequency and intensity of hurricanes, as well as their increased tendency to travel inland, is undoubtedly related to climate change.

Earlier this week, the Intergovernmental Panel on Climate Change released its Sixth Assessment Report.  The previous Assessment Report was released back in 2011.  Let's dive in and take a look at what they have to say, shall we? 

Helpfully, the Assessment Report starts with a Summary for Policymakers, an Executive Summary if you will.  It summarizes the current state of the climate with the frank observation that "It is unequivocal that human influence has warmed the atmosphere, ocean and land".  As a result of this warming, widespread and rapid changes in the atmosphere, ocean, ice caps, and biosphere have occurred. Some of these changes are summarized below in less technical jargon than used in the document and without all of the "likely," "very likely," and "extremely likely" qualifiers the careful scientists included in their report.

Temperature - Pre-industrial conditions were estimated from measurements between 1850 and 1900, the earliest observations sufficiently complete to estimate global surface temperature.  The last four decades have each been warmer than any previous decade since 1850.  Between 2010 and 2019, global surface temperature was 1.06°C (1.91°F) higher than the pre-industrial period (1850–1900), with larger increases observed over land (1.59°C/2.86°F) than over the ocean (0.88°C/1.58°F). 

While warming of the lower atmosphere due to greenhouse-gas emissions has been occurring, ozone depletion has simultaneously been cooling the higher stratosphere between 1979 and the mid-1990s. Greenhouse gases contributed an estimated 1.0°C to 2.0°C (1.8°F to 3.6°F) to the increased temperature, while other emissions (principally aerosols) may have cooled the surface by as much as 0.8°C (1.4°F) . 

Greenhouse Gas Concentrations - The increases in greenhouse-gas concentrations noted in the previous (Fifth) Assessment Report have continued since 2011. These increases are caused primarily by human activities, and in 2019, average annual greenhouse gas concentrations were:

• Carbon dioxide - 410 parts per million (19 ppm higher than 2011)
• Methane - 1,866 parts per billion (63 ppb higher than 2011)
• Nitrous oxide - 332 parts per billion (8 ppb higher than 2011)

The situation could be worse, except that over the past six decades, the land and ocean have absorbed nearly 56% of the global carbon-dioxide emissions from human activities each year. Unfortunately, land and ocean are not substantial sinks for greenhouse gases other than carbon dioxide, and we may be nearing the capacity of the amount of carbon dioxide the land and ocean can absorb.

Extreme Storm Events - The average annual precipitation over land has increased since 1950, with a faster rate of increase since the 1980s. Human influence has contributed to the increased precipitation, and to observed changes in near-surface ocean salinity. The tracks of mid-latitude storms (such as Tropical Storm Fred) have shifted poleward in both hemispheres since the 1980s. The global proportion of major (Category 3–5) hurricane and tropical cyclone occurrence has increased over the last four decades, and the latitude where tropical cyclones in the western North Pacific reach their peak intensity has shifted northward. However, long-term trends in the frequency of all categories of hurricanes and tropical cyclones cannot be determined based on current data.  Human-induced climate change increases heavy precipitation associated with hurricanes and tropical cyclones, but data limitations inhibit clear detection of past trends on a global scale.

Glaciers and Ice Caps - Human influence is very likely the main reason for the global retreat of glaciers since the 1990s and the decrease in Arctic sea ice area between 1979–1988 and 2010–2019. There has been no significant trend in Antarctic sea ice area from 1979 to 2020 due to regionally opposing trends and large internal variability. Human influence contributed to a decrease in Northern Hemisphere spring snow cover since 1950.  Human influence has contributed to the observed melting of the Greenland Ice Sheet over the past two decades, but there is only limited evidence of human influence on Antarctic Ice Sheet mass loss.

Oceans - It is virtually certain that the upper ocean has warmed since the 1970s due to human influence. It is virtually certain that human-caused carbon-dioxide emissions are the main reason for acidification of the open ocean.  Due to human influence, oxygen levels have dropped in many upper ocean regions since the mid-20th century. 

Sea Level - Global mean sea level increased by 0.20 meters (about 4 inches) between 1901 and 2018. The average rate of sea level rise was 1.3 millimeters per year (about 0.05 inches per year) between 1901 and 1971, increasing to 1.9 millimeters per year (about 0.07 inches per year)  between 1971 and 2006, and further increasing to 3.7 millimeters per year (about 0.15 inches per year) between 2006 and 2018. 

Biosphere - Changes in the land biosphere since 1970 are consistent with global warming: climate zones have shifted poleward in both hemispheres, and the growing season has on average lengthened by up to two days per decade since the 1950s in the Northern Hemisphere.

And all that's from just the first two pages of the Summary for Policymakers only and the Summary section goes on for 41 pages.  The entire report totals some 3,949 pages.   I've got a lot more reading to go.

Impermanence is swift, and all conditions are marked by constant change.  But the inevitability of change doesn't justify inaction or not protecting our planet, and by the way, did I mention Fred was coming?