evidence: For decades, CO2 concentrations at Mauna Loa in the month of May have broken previous records. But the recent acceleration in atmospheric CO2, surpassing a record-setting increase observed in 2016, is perhaps a more ominous signal of failing efforts to reduce global greenhouse gas emissions and the damage they cause to Earth’s climate. "Not only is CO2 still rising in the atmosphere — it’s increasing faster and faster," said Arlyn Andrews, a climate scientist at NOAA’s Global Monitoring Laboratory in Boulder, Colo. [...] Each annual maximum has raised new alarm about the curve’s unceasing upward trend — nearing 427 parts per million in the most recent readings, which is more than 50 percent above preindustrial levels and the highest in at least 4.3 million years, according to NOAA. Atmospheric CO2 levels first surpassed 400 parts per million in 2014. Scientists said in 2016 that levels were unlikely to drop below that threshold again during the lifetime of even the youngest generations.