The Global Impacts of Extremes
The Global Impacts of ExtremesPrioritize...
At the end of this section, you should be able to
- Interpret global changes in heat extremes, heavy precipitation, and drought
- Describe one way that scientists visualize trends and confidence in those changes.
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We’ve covered many extreme weather and climate concepts from a U.S. perspective, but how do these trends play out globally? The figure below (also, big version linked here) from the IPCC Sixth Assessment Report divides the world into regions (no, this isn’t a game of Settlers of Catan!). Each “tile” represents a region, such as ENA for Eastern North America. A team of scientists assessed changes in heat extremes, heavy precipitation, and drought since the 1950s, topics we’ve explored in this lesson. Tile colors indicate observed trends, while the number of dots represents the confidence scientists have that these trends are driven by human activity.
The top panel displays trends in hot extremes and confidence in human contributions. Red tiles show increases in hot extremes, blue shows decreases, dashed lines indicate unclear trends, and gray signifies limited data. Most regions show red tiles, supporting our earlier discussions on rising ratios of record highs to lows. High confidence (three dots) in many regions links these increases to greenhouse gas emissions and other human impacts.
The middle panel shows trends in heavy precipitation, with green for increases and brown for decreases. Most tiles are green, with trends pointing to more intense precipitation, as we discussed in North America. However, gray tiles in South America and Africa reveal gaps in data, underscoring why scientists advocate for better monitoring networks.
The bottom panel illustrates trends in agricultural and ecological drought (prolonged low precipitation). While heavy precipitation events have increased, drought trends are mixed, but most tiles are brown, indicating rising drought levels. How can heavy precipitation and drought both be on the rise? Timing is the key. In warmer climates, precipitation events cluster together, leading to long dry periods that stress water resources—a phenomenon known as the “boom-bust” cycle, where we see increasing shifts between very wet and very dry conditions.
