More on effects Bruce A. McCarl Distinguished Professor of Agricultural Economics Texas A&M University Energy Climate Change Adaptation Climate Change Mitigation Climate Change Effects

Reading Assignment IPCC WGII ar5 SPM pages 1-20 plus read sections labeleed reasons for concern

In recent decades, changes in climate have caused impacts on natural and human systems on all continents and across the oceans. Evidence of climate- change impacts is strongest and most comprehensive for natural systems. Bottom Line

Figure SPM.2 | Widespread impacts in a changing world. Map of effects

Risk of death, injury, ill-health, or disrupted livelihood in low-lying coastal zones and small island developing states, due to storm surges, coastal flooding, sea level rise. Risk of severe ill-health and disrupted livelihoods for large urban populations due to inland flooding in some regions. Systemic risks due to extreme weather events leading to breakdown of infrastructure and critical services such as electricity, water supply, health and emergency services. [RFC 2-4] Risk of mortality and morbidity during periods of extreme heat, particularly for vulnerable urban populations and those working outdoors in urban or rural areas.40 [RFC 2 and 3] Food insecurity and breakdown of food systems linked to warming, drought, flooding, precipitation variability and extremes, particularly for poor in urban and rural Loss of rural livelihoods/income due to insufficient drinking & irrigation water and reduced agricultural productivity, particularly for farmers with minimal capital in semi-arid regions. Risk of loss of marine and coastal ecosystems, biodiversity, and ecosystem goods, functions, and services for coastal livelihoods, especially for fishing communities in tropics and Arctic. Risk of loss of terrestrial and inland water ecosystems, biodiversity, and the ecosystem goods, functions, and services they provide for livelihoods. Source AR5 wgii spm Key Risks

Burning Embers – Reasons for Concern

Risks to Unique and Threatened Systems : “There is new and stronger evidence of observed impacts of climate change on unique and vulnerable systems (such as polar and high mountain communities and ecosystems), with increasing levels of adverse impacts as temperatures increase.”

Risks Associated with Extreme Weather Events : “Responses to some recent extreme events reveal higher levels of vulnerability. There is now higher confidence in the projected increases in droughts, heat waves, and floods, as well as their adverse impacts.”

Risks Associated with Aggregate Impacts : “Compared to the TAR, initial net market-based benefits from climate change are projected to peak at a lower magnitude of warming, while damages would be higher for larger magnitudes of warming.”

Risks Associated with the Distribution of Impacts : “There are sharp differences across regions and those in the weakest economic position are often the most vulnerable to climate change. There is increasing evidence of greater vulnerability of specific groups such as the poor and elderly not only in developing but also in developed countries. Moreover, there is increased evidence that low-latitude and less developed areas generally face greater risk, for example, in dry areas and megadeltas.”

Risks Associated with Large-Scale Discontinuities : “ There is high confidence that global warming over many centuries would lead to a sea level rise contribution from thermal expansion and ice that is projected to be much larger than observed over the 20th century, with loss of coastal area and associated impacts. “represents the likelihood that certain phenomena (sometimes called singularities or tipping points) would occur, any of which may be accompanied by very large impacts” For the Arctic region, new evidence indicates a biophysical regime shift is taking place rapid reduction of summer ice cover thawing of Arctic permafrost and shrub encroachment on the tundra widespread hydrological changes including lake formation or disappearance tundra food webs Reef building corals are in rapid decline irreversible loss of biodiversity increased mass bleaching of corals Dieback and degradation in the boreal forests and Amazonian rainforest increases in tree mortality including widespread dieback related to insect infestations and fire in North America (only low confidence in attribution to climate change) In humid tropical forests increased tree turnover (both mortality and growth) and enhanced drought risks interaction between climate change, deforestation, and fire

Burning Embers – Reasons for Concern

Table SPM.A1 | Observed impacts attributed to climate change reported in the scientific literature since the AR4. These impacts have been attributed to climate change with very low, low, medium, or high confidence, with the relative contribution of climate change to the observed change indicated (major or minor), for natural and human systems across eight major world regions over the past several decades. [Tables 18-5, 18-6, 18-7, 18-8, and 18-9] Absence from the table of additional impacts attributed to climate change does not imply that such impacts have not occurred. North America

For scenarios (RCP4.5, 6.0, and 8.5), ocean acidification poses substantial risks to marine ecosystems, especially polar ecosystems and coral reefs. Highly calcified mollusks, echinoderms, and corals are more sensitive than crustaceans (high confidence) and fishes (low confidence). Simultaneous drivers, such as warming and ocean acidification, can limpact for species and ecosystems. Figure SPM.6 B) Marine mollusk and crustacean fisheries and locations of corals, plus projected distribution of ocean acidification under RCP8.5. Bottom panel compares sensitivity to acidification across mollusks, crustaceans, and corals,. Number of species analyzed is given for each category of elevated CO2. For 2100, : RCP4.5 is 500–650 (approximately equivalent to ppm in the atmosphere), RCP6.0 for 651–850 and RCP8.5 for 851–1370. The control category corresponds to 380 μatm. Ocean Acidification