“This sense of instability is reinforced when we look within the last ice age at shorter-term climate fluctuations. There were repeated, incredibly rapid climate changes that were at least hemispheric in the extent of their impacts. As the last ice age ended, our record of these abrupt climate changes comes into sharper focus, revealing that warming of up to 10°C in Greenland has occurred within less than a decade. This reinforces the idea that the present climate system is unusually unstable—at least on relatively short timescales—providing an important backdrop for thinking about our own planet-changing activities as a species.”