Annual climate report finds that as CO2 continues to accumulate at an increasing rate, 2017 was among the hottest years on record
The world has experienced an increasing number of hot days since 1950, relative to the average for 1961-1990. (Source: NOAA Climate.gov, adapted from BAMS State of the Climate in 2017 Report) As abnormally warm temperatures continue to grip much of western North America, a new climate report finds that last year was the warmest on record that did not receive a temperature boost from El Niño. Considering all years, the 28th annual State of the Climate report confirms that in records dating back to 1880, 2017 saw the second or third highest global average temperature, depending on the dataset used. The cause? Carbon dioxide and other heat-trapping greenhouse gases we humans are pouring into the atmosphere. As noted in the report:
These and other findings from the peer-reviewed climate report, published as supplement to the Bulletin of the American Meteorological Society, are based on contributions from more than 500 scientists in 65 countries. Given the anomalous heat that has been gripping so much of North America in recent weeks, I thought I would mention one more finding: Last year saw an increase in the occurrence of warm temperature extremes, and reduced occurrences of cold extremes, compared to long-term averages. Although 2017 didn't bring a record high number of heat extremes, it still continues a long-term rising trend, as seen in the graph above.
The dominant greenhouse gases released into Earth’s atmosphere — carbon dioxide, methane, and nitrous oxide — increased once again in 2017, reaching new record highs.
Even more unsettling: The global growth rate of carbon dioxide has nearly quadrupled since the early 1960s. In other words, efforts to curtail emissions have not yet proven effective. The average global concentration of CO2 in the atmosphere was 405 parts per million, according to the report. This was not only the highest in the modern 38-year global record, it is also the highest seen ice-core records dating back as far as 800,000 years.