Michael E. Mann is distinguished professor of atmospheric science and director of the Earth System Science Center at Penn State University. He is author of the recently released bookn April 22 of 1998, the warmest year that had yet been observed, my co-authors and I published the now famous “hockey stick” curve.
Reconstructions of past El Niño behavior based on climate proxy data provide an important opportunity, for example, to revisit a controversial hypothesis linking explosive tropical volcanic eruptions and historical El Niño events—a hypothesis that has profound implications for the impact climate change may have on drought in the desert southwest and Atlantic hurricane activity.
Climate models project this ocean current system to slow down later this century. But an analysis of paleoclimate proxy data spanning the common era suggests that the slowdownthis past century, likely because the Greenland ice sheet is melting earlier than expected. So, we may be well ahead of schedule when it comes to this unwelcome climate system “tipping point,” a reminder that uncertainty is not our friend when it comes to the unfolding impacts of human-caused warming.
Last but not least, what do data and simulations of the common era tell us about how near we are to the threshold of truly dangerous planetary warming? The conventional estimate is that we must reduce carbon emissions by 50% by the end of this decade to avoid 1.5°C warming over pre-industrial levels, where we’re likely to see far worse climate consequences.
The hockey stick emphasizes the relative stability of the global climate over the common era, the period during which much of our civilizational infrastructure was developed. But evidence is growing that suggests we are rapidly leaving this era of climate stability—we find now ourselves in what I’ve termed our “.” There is still time to preserve that moment, but only if act with the urgency the climate crisis demands.