Marine heatwaves have approximately doubled 
74 
‘Main driver’ means responsible for more than 50% of the change. {WGI SPM footnote 12}
75 
See Annex I: Glossary.
in frequency since the 1980s (high conﬁdence), and human inﬂuence 
has very likely contributed to most of them since at least 2006. The 
frequency and intensity of heavy precipitation events have increased 
since the 1950s over most land areas for which observational data 
are sufﬁcient for trend analysis (high conﬁdence), and human-caused 
climate change is likely the main driver (Figure 2.3). Human-caused 
climate change has contributed to increases in agricultural and ecological 
droughts in some regions due to increased land evapotranspiration 
(medium conﬁdence) (Figure 2.3). It is likely that the global proportion 
of major (Category 3–5) tropical cyclone occurrence has increased over 
the last four decades. {WGI SPM A.3, WGI SPM A3.1, WGI SPM A3.2; 
WGI SPM A3.4; SRCCL SPM.A.2.2; SROCC SPM. A.2}
Climate change has caused substantial damages, and increasingly 
irreversible75 losses, in terrestrial, freshwater, cryospheric and 
coastal and open ocean ecosystems (high conﬁdence). The extent 
and magnitude of climate change impacts are larger than estimated 
in previous assessments (high conﬁdence). Approximately half of the 
species assessed globally have shifted polewards or, on land, also to 
higher elevations (very high conﬁdence). Biological responses including 
changes in geographic placement and shifting seasonal timing are often 
not sufﬁcient to cope with recent climate change (very high conﬁdence). 
Hundreds of local losses of species have been driven by increases in 
the magnitude of heat extremes (high conﬁdence) and mass mortality 
events on land and in the ocean (very high conﬁdence).