Lecture 2: WIC is Climate Change Really Dangerous

WIC: Future Climates: Science and Impacts - Is climate change really dangerous? Climate change in the media All the facts agree that climate change is real and it is human induced The Greenhouse Effect – changing the composition of the atmosphere is going to change our climate Infrared radiation gets trapped Brief History of Global Warming Research: Foote? Tyndall (1820-1893) – explained heat in the earth’s atmosphere in terms of various gases in the air to absorb infrared radiation, particularly water vapour Arrhenius (1859-1927) – fossil fuel combustion may result in enhanced global warming. A doubling of CO2 concentration would lead to a 5C temperature rise Observed CO2 changes – increasing Last time we experienced CO2 this high was 3 million year ago Studies able to pinpoint what is natural change and what is human induced change for CO2 levels Surface air temp increasing 1950s Observed emissions and possible future emissions - hard to predict The emission pledges submitted to the Paris climate summit currently put us roughly on the brown RCP 6.0 scenario How can we predict the impact of these projected changes on future climate? Computer climate models: - Similar to weather forecast models - They are based on the physics of climate, but require approximations - Tested against past (100 years and also 10,000’s of years) Physics of climate Still have to make approximations – so not perfect Test the models using past climate change Projections of temperature change RCP – representative concentration pathway Regions may cool – turns off ocean circulation Cumulative emission are the key - Cumulative emissions of CO2 largely determine global warming - Climate change will persist - This represents a substantial commitment to addressing climate change Projections of precipitation change – variability – by large wet places will get wetter, dry will get drier – amplify existing patterns of precipitation There is a lot of differences, special patterning Regional changes (especially hydrological) more uncertain – more change and uncertainty When did climate change become dangerous? ‘Climate change could bring the planet to the edge of anarchy… the threat to global stability vastly eclipses that of terrorism’ - Pentagon report 2004 Politicians forced scientists to define what dangerous climate change is – not a scientific question Types of impact, systems: water, ecosystems, food, coast, health, singular events Increasingly 1.5C is the transition to ‘dangerous’ Burning Embers diagrams attacked for choice of colours (using red shows danger) Impacts on Human Health (rising temp, weather extremes, rising seas levels): ● Increased heat – heat stress, cardiovascular failure ● Severe weather – injuries, fatalities ● Vector borne diseases – malaria, dengue, encephalitis, hantavirus, Rift valley fever ● Allergies – respiratory allergies, poison ivy ● Water-borne diseases – cholera ● Environmental refugees – forced migration, civil conflict ● Water and food supply – malnutrition, diarrhoea, harmful algal blooms ● Mental health – anxiety, despair, depression, post-traumatic stress ● Air pollution – asthma, cardiovascular disease WHO report in 2002 estimated 150,000 deaths/yr due to climate change Compared to smoking deaths 4.83m Malaria deaths 1m August 2003 heat wave Maximum daily temps 36C around 9 days (France) 30-50,000 deaths in Europe Mean temps 5C above 1988-2003 average Peak mortality lagged onset of high temperatures (peak mortality 2,200 deaths/day) No harvesting effects Heat wave was maybe not due to climate change Heat wave duration index, defined as the max period of at least 5 consecutive days with maximum temperature higher by at least 5C than the climatological norm for the same calendar day (no universally accepted definition of heat wave) By 2080 this would be a cool summer This would be the average summer by 2050 if we exceed Paris agreement targets Problem with the 2003 heat wave was that we weren’t prepared UK dept of health: · 25% chance of a heat wave in next 10 years which will kill 3000 · Compared to the 20,000 deaths a year from cold (-33% over 1971-2003) · But 14.5% increase in salmonella poisoning · Air pollution deaths are currently considerably more important with a projected increase of 4% by 2030s · Water quality and mental health issues associated with flooding · Increased UV exposure (extra 5000 cases increase in skin cancer and 2000 cataracts/year by 2050) · Small risk from malaria, ticks, Lymes disease Malaria predictions 2080 · 90-200m more exposed · Up to 500,000 additional deaths (currently 450 million cases annually and 1 million deaths) · Temperature and changes of moisture The Economics of Climate Change Lords select committee produced a report on the “Economics of Climate Change” in 2005- concluded that the science of climate change was so uncertain that there was no economic case to consider Government disagreed and commissioned Lord Stern to produce a review in 2006 (key question regarding mitigation costs) · · · He argued that it is global, long-term, uncertain and potentially large and irreversible Possibility for large tipping points Stern concluded that the discount rate was very low (the discount rate converts future economic impacts into their present day value) Spend money to benefit in long term – what’s the cost of mitigating climate change and the impact of it Estimating economic impacts Convexity Distribution of impacts: developing countries are especially vulnerable, developed countries are not immune Could have extreme events and large scale abrupt irreversible events Aggregate impacts of climate change: · Worst case scenario 13.8% loss in GDP by 2200, baseline 5.3% · Could cost up to 20% GDP · Expected cost of cutting emissions consistent with a 550ppm CO2e stabilization trajectory is 1% (+/- 3%) of GDP in 2050 Strong mitigation is fully consistent with the aspirations for growth and development in poor and rich countries. Business as usual is not. Costs will not be evenly distributed: - Competitiveness impacts can be reduced by acting together - New markets will be created. Investment in low-carbon electricity sources could be over $500bn a year by 2050 Mitigation policy can also be designed to support other objectives: - Energy – air quality, energy security and energy access - Forestry – watershed protection, biodiversity, rural livelihoods Stern’s conclusion - The cost of mitigation of climate change is about 1% of global GDP per year. - Unabated climate change impacts could cost up to 20% of global GDP - Hence, we should immediately invest 1 percent of world economic activity to reduce the impact of global warming. - Failing to do so could risk future economic damages equivalent to a reduction of up to 20 percent in global G.D.P. - Action is urgent: delay means greater risks and higher costs. - BUT IPCC (2014) comments that “Global economic impacts from climate change are difficult to estimate.” - And IPCC Special Report (2018) comment: “Total annual average energyrelated mitigation investment for the period 2015 to 2050 in pathways limiting warming to 1.5°C is estimated to be around 900 billion USD2015” - “… (costs) are roughly 3-4 times higher than in pathways limiting global warming to below 2°C