How summertime temperature variability will change with warming has important implications for climate adaptation and mitigation. CMIP5 simulations indicate a compound risk of extreme hot temperatures in western Europe from both warming and increasing temperature variance. CMIP6 simulations, however, indicate only a moderate increase in temperature variance that does not covary with warming. To explore this intergenerational discrepancy in CMIP results, we decompose changes in monthly temperature variance into those arising from changes in sensitivity to forcing and changes in forcing variance. Across models, sensitivity increases with local warming in both CMIP5 and CMIP6 at an average rate of 5.7 ([3.7, 7.9]; 95% c.i.) × 10−3°C per W m−2per °C warming. We use a simple model of moist surface energetics to explain increased sensitivity as a consequence of greater atmospheric demand (∼70%) and drier soil (∼40%) that is partially offset by the Planck feedback (∼−10%). Conversely, forcing variance is stable in CMIP5 but decreases with warming in CMIP6 at an average rate of −21 ([−28, −15]; 95% c.i.) W2 m−4per °C warming. We examine scaling relationships with mean cloud fraction and find that mean forcing variance decreases with decreasing cloud fraction at twice the rate in CMIP6 than CMIP5. The stability of CMIP6 temperature variance is, thus, a consequence of offsetting changes in sensitivity and forcing variance. Further work to determine which models and generations of CMIP simulations better represent changes in cloud radiative forcing is important for assessing risks associated with increased temperature variance.
The increasing frequency of very high temperatures driven by global warming has motivated growing interest in how the probability distribution of summertime temperatures will evolve in the future. Climate models forced by increasing CO
- NSF-PAR ID:
- 10455559
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 47
- Issue:
- 19
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Widespread changes in arctic and boreal Normalized Difference Vegetation Index (
NDVI ) values captured by satellite platforms indicate that northern ecosystems are experiencing rapid ecological change in response to climate warming. Increasing temperatures and altered hydrology are driving shifts in ecosystem biophysical properties that, observed by satellites, manifest as long‐term changes in regionalNDVI . In an effort to examine the underlying ecological drivers of these changes, we used field‐scale remote sensing ofNDVI to track peatland vegetation in experiments that manipulated hydrology, temperature, and carbon dioxide (CO 2) levels. In addition toNDVI , we measured percent cover by species and leaf area index (LAI ). We monitored two peatland types broadly representative of the boreal region. One site was a rich fen located near Fairbanks, Alaska, at the Alaska Peatland Experiment (APEX ), and the second site was a nutrient‐poor bog located in Northern Minnesota within the Spruce and Peatland Responses Under Changing Environments (SPRUCE ) experiment. We found thatNDVI decreased with long‐term reductions in soil moisture at theAPEX site, coincident with a decrease in photosynthetic leaf area and the relative abundance of sedges. We observed increasingNDVI with elevated temperature at theSPRUCE site, associated with an increase in the relative abundance of shrubs and a decrease in forb cover. Warming treatments at theSPRUCE site also led to increases in theLAI of the shrub layer. We found no strong effects of elevatedCO 2on community composition. Our findings support recent studies suggesting that changes inNDVI observed from satellite platforms may be the result of changes in community composition and ecosystem structure in response to climate warming. -
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Abstract Anthropogenic climate change compromises reef growth as a result of increasing temperatures and ocean acidification. Scleractinian corals vary in their sensitivity to these variables, suggesting species composition will influence how reef communities respond to future climate change. Because data are lacking for many species, most studies that model future reef growth rely on uniform scleractinian calcification sensitivities to temperature and ocean acidification. To address this knowledge gap, calcification of twelve common and understudied Caribbean coral species was measured for two months under crossed temperatures (27, 30.3 °C) and
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Abstract Aim High‐elevation plants are disproportionally affected by climate change. As temperatures rise, the amount of available alpine habitat in the Rocky Mountains will decrease resulting in potential local extinctions of plant species. In addition to the direct effects of climate‐driven habitat loss, alpine plants must also respond to indirect effects, such as changes in disturbance regimes. One notable shift is the increase of wildfire frequency in regions where fire was previously rare or absent, including the alpine. We hypothesized that direct climatic changes compounded with increased wildfire frequency will reduce the future suitable habitat of high‐elevation plants more than if climate was considered alone.
Location Rocky Mountain Floristic Region, western North America.
Taxon Saxifraga austromontana (Saxifragaceae), a wildflower endemic to high elevations of the Rocky Mountain Floristic Region.Methods Our approach integrated historical herbarium records, field surveys, remote sensing, species distribution models, historic wildfire data, and predictive models.
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