Improved Homogenisation of Observations Shows Steadier and Faster Historical Global Warming

Instrumental climate records are foundational for understanding Earth's climatic history, yet the task of estimating Earth's surface temperatures since 1850 —- through data gathered from an extensive network of terrestrial weather stations and oceanic voyages -— presents substantial challenges. Specifically, early temperature measurements contain biases and errors from diverse sources, complicating efforts to achieve a consistent and homogeneous dataset.

In this talk, I will review the history and recent advances in statistical methods for homogenising ocean and land temperature records, as well as the inter-calibration across these two data archives.  These methodological advancements improve the accuracy of detecting, estimating, and adjusting data biases.  Multiple lines of evidence including metadata, physical knowledge, paleo proxies, and historical documents are used to check the results of these statistical analyses.

Applying these methodological advancements, we first homogenise ocean and land temperature archives individually and then across the two archives to obtain a Dynamically Consistent ENsemble of Temperature (DCENT). DCENT shows a steadier and 10% larger increase in global mean surface temperatures since 1850.  The steadier warming in DCENT better aligns with the expected temperature responses to external radiative forcing, implying a reduced role for internal variability in historical warming patterns.  The greater warming points to an earlier surpassing of the 1.5°C target set forth in the Paris Agreement, with five-year-average temperatures expected to exceed this threshold by 2029.

Despite these advancements, opportunities exist to further improve the accuracy and completeness of historical climate records. Future efforts could involve the continued rescue of data and metadata, improving regional reconstructions, and better integrating instrumental records and paleo proxies. Equally important, extending homogenisation to encompass multiple types of climate records, for example, temperature and sea-level pressure, promises to yield a more coherent understanding of historical climate variations. Together, these avenues of research hold the potential to further refine our understanding of Earth’s historical climate and better inform climate projections.

Watch a recording of this talk.

Short Bio:
I am a climate scientist and a lecturer in the School of Ocean and Earth Science at the University of Southampton. Before relocating to the UK, I served as a Postdoctoral Scholar at WHOI, subsequent to earning my Ph.D. from Harvard University.  My research focuses on developing statistical and physical tools to quantify and elucidate the mechanisms underlying climate change. I led the development of the Dynamically Consistent Ensemble of Temperature (DCENT). I have published papers in Nature, Nature Food, Science Advances, Journal of Climate, and other top-tier journals in Earth and Climate Sciences. My work has been featured by NPR, Science, and other international media.