Pollen-reconstructed New Brunswick (Canada) spring temperatures affirm the Medieval Warm Period or Medieval Climate Anomaly (MCA, 900-1400 CE) was 1°C warmer (3.2°C vs. 2.2°C) than both the Little Ice Age (LIA, 1400-1850 CE) and modern period (1850 to present).

Other sites in this region also show no net warming since the 1800s and 1-3°C cooling from the MCA to the LIA.

This new research also identifies a higher frequency of natural forest fires during the LIA cooling period than the warmer MCA.

Image Source: Collins et al., 2026