For the 23rd year, researchers have compiled a “state of the climate” report—and as report cards go, it’s not a good one. Using data from satellites, buoys, and weather stations worldwide, 384 scientists from 52 countries looked at various trends in temperature, precipitation, sea ice, and greenhouse gas concentrations, to name a few. Atmospheric concentrations of planet-warming carbon dioxide reached a record 392.6 parts per million in 2012, the researchers report online today in the Bulletin of the American Meteorological Society. Last year also posted records for carbon dioxide emissions (including an estimated 9.7 billion metric tons of carbon), the heat-trapping effect of major greenhouse gases, including CO 2 , methane, and nitrous oxide (up 32% since 1990), and sea-level rise (up an average of 68 millimeters globally since 1993). The Arctic is warming about twice as fast as the rest of the world, the researchers note, and accordingly the effects there are particularly pronounced. In September, the area covered by Arctic sea ice (image) reached a new low of 3.4 million square kilometers—an area about twice the size of Alaska and a whopping 18% below the previous record set in 2007. June snow cover on land in the Arctic (a climate measure that’s now declining faster than sea ice) also reached a new low in 2012, and permafrost temperatures in northernmost Alaska reached new highs. Overall, 2012 was one of the 10 warmest years on record—and wasn’t warmer thanks to the lack of an El Niño. (That climate phenomenon results when sea-surface temperatures in the equatorial Pacific climb more than 0.5°C above normal for an extended period, triggering changes in weather patterns and generally boosting global temperatures in the process.)