The world's top 5 warmest years on record have occurred since 2014 — and it's almost certain that 2019 will be added to this list as well.
Why it matters: Such trends are indicative of long-term global warming due to human activities such as burning fossil fuels for energy and transportation, cutting down forests for agriculture and other purposes. Only 1 of the top 20 warmest years on record since instrument data began in 1880 took place before the year 2000. With greenhouse gas concentrations in the air at their highest level in 3 million years, the odds favor more record-shattering years in the future.
