November 4, 2017

Here is a classic case of bipolar behavior. The Trump Administration withdrew from COP21 on the belief that it hurts the economic interests of the United States. Today however, over a dozen agencies of the very same government jointly released the congressionally mandated Climate Science Special Report. In it, hundreds of scientists conclude “based on extensive evidence, that it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20^th century.” Here are some consequences of climate change:

• Global annually averaged surface air temperature has increased by about 1.0˚C (1.8˚F) between 1901 and 2016, the warmest period in the history of modern civilization.
• Thousands of studies conducted by researchers around the world have documented changes in surface, atmospheric, and oceanic temperatures; melting glaciers; diminishing snow cover; shrinking sea ice; rising sea levels; ocean acidification; and atmospheric water vapor.
• Global average sea levels are expected to continue to rise in the next 15 years and by approximately 1 meter (1-4 feet) by 2100. A rise of as much as 2.4 m (8 feet) cannot be ruled out.
• Heavy rainfall in the Northeast of the United States and in some areas globally is increasing in intensity and frequency and is expected to continue to increase.
• Heatwaves have become more frequent in the United States since the 1960s, while extreme cold temperatures and cold waves are less frequent.
• The incidence of large forest fires in the western United States and Alaska has increased since the early 1980s and is projected to further increase in those regions as the climate changes, with profound changes to regional ecosystems.
• Annual trends toward earlier spring melt and reduced snowpack are already affecting water resources in the western United States and these trends are expected to continue. Under higher scenarios, and assuming no change to current water resources management, chronic, long-duration hydrological drought is increasingly possible before the end of this century.
• The magnitude of climate change beyond the next few decades will depend primarily on the amount of greenhouse gases (especially carbon dioxide) emitted globally. Without major reductions in emissions, the increase in annual average global temperature relative to preindustrial times could reach 5˚C (9˚F) or more by the end of this century. With significant emissions, the increase in annual average global temperature could be limited to 2˚C (3.6˚F) or less.
• The global atmospheric carbon dioxide (CO₂) concentration has now passed 400 parts per million (ppm), a level that last occurred about 3 million years ago, when both global average temperature and sea level were significantly higher than today. Continued growth in CO₂ emissions over this century and beyond would lead to an atmospheric concentration not experienced in tens to hundreds of millions of years. There is a broad consensus that the further and the faster the Earth system is pushed towards warming, the greater the risk of unanticipated changes and impacts, some of which are potentially large and irreversible.
• The observed increase in carbon emissions over the past 15–20 years has been consistent with higher emissions pathways. In 2014 and 2015, emission growth rates slowed as economic growth became less carbon-intensive. Even if this slowing trend continues, however, it is not yet at a rate that would limit global average temperature change to well below 2°C (3.6°F) above preindustrial levels.

The report does not estimate the cost of climate change to the United States, nor does it compare it with the cost of leaving fossil fuels in the ground, which is what it would take to stop the flow of CO₂ into the atmosphere. However the losses from the recent (and future) furious hurricanes, forest fires, drought, and the inexorable depletion of aquifers in the Great Plains and California, the source of much of our food, are a clear and present danger to the nation’s very security. First we lost our manufacturing base; now we’re on track to lose our ability to grow our own food. Along with the growing threat of thermonuclear war, these issues should be the talk of the town, but they aren’t. Instead, people who aren’t even born yet will face the music –and curse us for our irresponsible greed.