Sea Surface Temperature Biases Shift North Pacific Jet Stream Southward

Climate models, which numerically simulate the atmosphere, oceans, and other components of the Earth system, are the primary tools for projecting future climate change. By integrating physical equations from the present into the future, these models generate predictions of temperature, precipitation, and other climate variables under various scenarios. However, even when run for the current period, many models fail to reproduce observed climate patterns exactly, exhibiting systematic biases in temperature, rainfall, or sea‑level rise.

The sources of these biases—such as imperfect representations of cloud processes, land‑surface feedbacks, or ocean circulation—also influence the models’ future projections. When a model misrepresents present‑day conditions, its extrapolation into the future can be skewed, potentially under‑ or over‑estimating the magnitude of climate change. Consequently, researchers focus on diagnosing and correcting present‑day biases to enhance the credibility of long‑term forecasts, ensuring that policy decisions are based on the most reliable projections available.