Ancient climates reveal sharply different wetting by latitude
A peer-reviewed study combined ancient climate records with simulations to trace moisture changes since the last ice age. Northern high latitudes generally became wetter, while some mid-latitude regions were wetter in cold periods and monsoon regions in warm periods. Its future simulations show another uneven map of wetting and drying, but the ancient climate is no direct forecast of today's warming.
Science··Evening
The ancient moisture map splits by latitude
A peer-reviewed study in Communications Earth & Environment traces changes in land moisture since the last glacial maximum, roughly 21,000 years ago. Research Today also reports its central result: high northern latitudes generally became wetter, while some mid-latitude regions were wetter in cold periods and low-latitude monsoon regions in warm periods. The pattern rules out one worldwide direction of moisture change during the transition out of the ice age.[1], [2]
Records and models answer different questions
The researchers combined 191 ancient-climate records with 16 palaeoclimate models and a simulation that follows climate through the transition. They compared rainfall minus evaporation with a separate virtual-lake calculation that estimates changes in stored water. Those measures are related but do not mean the same thing. Their directional agreement varied across the period comparisons, and some locations in southern Africa and South America showed disagreement between model output and physical climate indicators.[1]
Future projections retain the regional divide
Under a high-emissions scenario, the study’s future simulations project drying across many subtropical and mid-latitude areas and wetting in high latitudes and monsoon regions. The authors compared different forcing experiments, including ice sheets, greenhouse gases and orbital conditions, to examine why the ancient pattern arose. Because those ancient conditions differ from today’s, past changes are evidence for the mechanisms, not a direct forecast of future local rainfall.[1]
