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Diurnal temperature range (DTR) declined over global land during 1950-2004. Climate model simulations have shown DTR is sensitive to many forcings including solar radiation, CO2, aerosols and land cover change. Relationships between DTR trends and potential forcings or feedbacks fall short of providing causal evidence due to paucity of observations and a focus on average changes over the diurnal cycle rather than changes within the diurnal cycle. Non-linear regression of seasonal and geographic variations in DTR found cloud cover, soil moisture, distance inland, solar radiation, elevation and vegetation type explained 80% of the variation in DTR. These factors are likely influential for regional DTR trends. Surface net longwave radiation was linearly related to seasonal variations in DTR and explained over 95% of the' variation in tropical regions. The NCAR SCCM model was used to simulate the response of DTR and surface energy fluxes to 2 x CO2 and -2% solar forcings. An ensemble of 24 model runs with forcing applied hourly through the diurnal cycle was replicated 20 times in 18 locations. Under CO2 forcing, the increase in DTR at the first '.···r time-step after forcing (0.01 DC) was offset by rapid adjustments and climate feedbacks during the three-day period after forcing. Rapid adjustments to surface sensible and latent heat fluxes totalled +1.55 Wm·2 driven by tropospheric adjustments to clouds and humidity. Under solar forcing, the reduction in DTR at the first time-step after forcing (-0 .l5DC) was subsequently magnified (-0 .l7DC) by feedbacks. Rapid adjustments were dominated by a reduction in surface sensible heat (-1.39 Wmo2) offset by an inversely correlated increase in surface latent heat (+0.98 Wmo2). There was no evidence of a tropospheric rapid adjustment with solar forcing. CO2 induced diurnal changes in downwelling longwave radiation and rapid adjustments in surface heat fluxes have likely contributed to the global DTR trend. 7 1 I

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Predicting the consequences of extinction is an important goal in ecology, due to the accelerating rate of global and local species loss. Cascading extinction~ the extinction of one species as a consequence of the extinction of another, has been demonstrated in several natural ecosystems and is widely predicted by theoretical studies. Extinction may also affect the functioning of ecosystems, as functionally important species may be lost from communities and positive interactions between species may be disrupted. Investigating the consequences of extinction in natural ecosystems is difficult, as removing a species from an area of habitat is often problematic. Also, because indirect effects may take many generations to be revealed, experimental manipulations in natural ecosystems often need to last for several years. Experimental aquatic microcosms provide a new opportunity for conducting removal experiments in small, tractable, communities containing rapidly reproducing species. Here, I present the results of four experiments conducted in such microcosms that . investigated the consequences of the removal ofa species and the effect of temperature and energy on patterns ofextinction. In general, local diversity was robust to the removal of a species. No cascading extinction was observed and some positive effects of extinction for diversity were revealed. Species loss had a positive, negative or no effect on ecosystem functioning, depending upon community composition. Small changes to the identity of the species present in communities had large effects; the consequences of extinction for . . ecosystem functioning was very context-dependent and rare species were important. Temperature and chemical energy interacted to determine species diversity and extinction determinism, making it difficult to predict the consequences of changes to either temperature or chemical energy for extinction without knowledge of the other.

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