For decades, the rise in Earth's average temperature has appeared to follow a fairly consistent upward path. Individual years have stood out because of events such as strong El Niño episodes or volcanic eruptions, but the broader trend seemed relatively stable.

Rate nearly double the 1970-2015 average; 1.5°C threshold could be breached before 2030 if trend continues

For decades, the rise in Earth's average temperature has appeared to follow a fairly consistent upward path. Individual years have stood out because of events such as strong El…