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Climate Change - Why Should we Care
- 2. Climate Change: Why Should You Care? Dr. Colin Fenwick & Ian Stewart
- 3. This Evening’s Lecture:- • The evidence for warming (thermometers, not computer models) • How remarkable are recent trends? • Hasn’t climate always changed? • Why should you care?
- 4. What is the Evidence for Warming? • Land temperatures are recorded daily by a global network of fixed weather stations.
- 5. What is the Evidence for Warming? • Ocean temperatures historically collected by ships and buoys but since 2000 have increasingly been collected by ARGO floats. • ARGO is a global array of free-drifting floats that measure the temperature and salinity of the upper 2km of the ocean.
- 6. What Happens to All the Raw Data? • Compiled into global temperature records by a number of different independent scientific bodies. • The best known are :- • NASA GISS (Goddard Institute for Space Studies) • NOAA NCEI (National Centre for Environmental Information) • HadCRUT (UK Met Office Hadley Centre & The Climate Research Unit at UEA)
- 7. What Happens to All the Raw Data? • Corrections made for instance… • Land stations not evenly spread across the globe. Interpolation required for areas with poor coverage. • Station has moved, changed its equipment or environment changed over time (heat island effect). • Arctic has poor coverage but is warming rapidly. Each body treats the Arctic differently leading to subtle differences.
- 8. NASA, NOAA & HadCRUT, 1880-2015
- 9. Surface Temperature 1880-2016 YTD Jan-August 2016 Baseline 1951 to 1980
- 10. Has Any Other Check Been Made? • In 2012 physicist Richard Muller set up the Berkeley Earth Surface Temperature to provide an additional temperature series. • Muller was regarded as something of a sceptic, he was on record casting doubt on the existing surface temperature reconstructions. • BEST used the same thermometer dataset but developed their own processing. • When the BEST temperature series was published it was essentially identical to those already in existence.
- 11. BEST Comparison 1980-2013 (video 4min 40sec)
- 12. BEST Temperature Series 1850-2015
- 13. Is There Any Other Useful Thermometer? • Ocean volume increases due to thermal expansion in a warming world – raising sea level • Greenland ice melts in a warming world – raising sea level • Antarctic ice melts in a warming world – raising sea level • Glaciers worldwide melt in a warming world – raising sea level • The reverse of this happens in a cooling world – lowering sea level • Hence changes in sea level are an excellent indicator of climate change, just like mercury in a thermometer.
- 14. Sea Level 1993 – Present (Satellites) Satellite measurements remove the need to take land movements into account but only go back to 1993. Flooding in Pakistan and Australia in 2011
- 15. Sea Level 1870 – 2013 (Gauges + Satellites) Tide stations + satellite data composite
- 16. High Tide in Miami
- 17. • Thermometer records show it • Accelerating sea level rise shows it • Rapidly reducing Arctic sea ice • 90% of mountain glaciers are melting • Accelerating Greenland melt • Accelerating melt in Western Antarctic • Loss of ice shelves which have been stable since the last ice age • Spring flowers bloom earlier, Species habitat moving poleward… There is no doubt the planet is warming. The question is whether this is our doing or is it just part of the natural background variation? The Planet is Warming!
- 18. How Remarkable are Recent Trends? • Reliable thermometer records only extend back to ~ 1880. • But temperature proxies such as :- • Ice cores • Tree rings • Corals • Speleothems (stalactites & stalagmites) • Allow temperature reconstructions going back many thousands of years. • In 1999 Mann et al published a temperature reconstruction going back 1000 years.
- 19. How Remarkable are Recent Trends? Diagram from the Third IPCC Assessment Report 2001
- 20. Kangiata Nunata Sermia Glacier, SW Greenland Glacier top ~ 1850 2010
- 21. Changes in Greenland 1933-2013
- 22. OK but Hasn’t the Climate Always Changed? Of course, but always in response to something. So what is driving the recent warming?
- 23. So What are the Natural Drivers? • The brightness of the sun
- 24. Brightness of the Sun Surface temperature (red) keeps rising. The Sun’s output (blue) follows a recognised 11 year cycle.
- 25. So What are the Natural Drivers? • The brightness of the sun – can’t explain recent warming • Periodic changes in the Earth's orbit (global wobbling)
- 26. Periodic Changes in the Earth's Orbit • Eccentricity - 100,000 year period.
- 27. Periodic Changes in the Earth's Orbit • Obliquity - 41,000 year cycle which exaggerates seasonality
- 28. Periodic Changes in the Earth's Orbit • Precession – 26,000 year cycle
- 29. Periodic Changes in the Earth's Orbit • Far too slow to explain recent warming, changes occur gradually over thousand year timescales. • The planet should currently be cooling.
- 30. So What are the Natural Drivers? • The brightness of the sun – can’t explain recent warming • Periodic changes in the Earth's orbit - can't explain recent warming • Albedo
- 31. So What are the Natural Drivers? • The brightness of the sun – can’t explain recent warming • Periodic changes in the Earth's orbit - can't explain recent warming • Albedo (secondary effect) • Volcanoes
- 32. So What are the Natural Drivers? • The brightness of the sun – can’t explain recent warming • Periodic changes in the Earth's orbit - can't explain recent warming • Albedo (secondary effect) • Volcanoes (lowers temperature for a few years after a big eruption) • Arrangement of the continents
- 33. So What are the Natural Drivers? • The brightness of the sun – can’t explain recent warming • Periodic changes in the Earth's orbit - can't explain recent warming • Albedo (secondary effect) • Volcanoes (lowers temperature for a few years after a big eruption) • Arrangement of the continents (important over very long periods) • Greenhouse effect
- 34. The Greenhouse Effect • The heat trapping effects of water vapour, CO2 and methane in the atmosphere were demonstrated in the mid-19th century. Without the greenhouse effect the Earth’s surface temperature would be approximately 30° C cooler than it actually is. A powerful greenhouse effect makes Venus the hottest planet in the solar system despite being farther from the Sun than Mercury.
- 35. Greenhouse Effect Smoking Gun
- 36. Atmospheric CO2 last 1000 years…another hockey stick! Pre-industrial ~ 280ppm 2015 – 401 ppm and rising 2016 – 404 ppm and rising
- 37. Why Should We Care? Weather extremes will occur more frequently, floods, droughts, storms. Sea level rise will continue to accelerate, displacing millions of people. Landscape and ocean chemistry changes will alter what we can grow, catch and eat. Displacing populations. Humanity has lived through climate shifts before but not with the fixed infrastructure and intensive food production we have today.
- 38. What was Decided in Paris? • Countries aim to limit temp rise to well below 2° C whilst pursuing efforts to stay within 1.5° C. • But, pledges imply a rise this century of ~3.0 - 3.5° C above pre- industrial. • Nothing legally binding, will rely on 5 year reviews and peer pressure to ramp up action.
- 39. Reality • 2015 saw the temperature rise reach ~1° C over pre-industrial. In late 2016 it looks more like 1.3° C. • Staying below 1.5° C is not realistically possible. • Even with an extremely aggressive shift to renewables it is highly unlikely we will keep temperature rise to within 2° C over pre- industrial. • Can we go back 25 years?
- 40. What Can We Do? • Become knowledgeable about the issue and the solutions. • Actively push politicians to make the right choices. • Move out of any investments that include fossil fuels. • Save yourself money by… • Get free smart meters fitted by your power company • Have at least one meat free day a week (healthy) • Get your home better insulated (warmer) • Walk or cycle short distances (healthy) • Try to live more sustainably (cheaper) • Support the green economy (worth £128 billion and 270,000 jobs, DECC)
- 42. Carbon Budgets • Since the mid-18th-century, humanity has pumped around 2,100 billion tonnes of CO2 into the atmosphere. • This has increased the concentration of CO2 in the atmosphere from 280 PPM to 404 PPM and raise the temperature ~1.3° C. • Mankind currently emits around 40 billion tonnes of CO2 into the atmosphere each year. • To have a 66% chance of keeping rise to <1.5°C we can emit no more than a further 200 billion tonnes CO2. • To have a 66% chance of keeping rise to <2° C we can emit no more than 800 billion tonnes CO2.
- 43. Surface Temperature 1880-2016 YTD Jan-August 2016 Baseline 1951 to 1980
Editor's Notes
- Ian to introduce himself and explain that the lecture was put together by Colin but Is really a collaborative work given that Colin isn't in a position to present the lecture. Colin will however endeavour to answer any questions at the end.
- This evenings lecture will be divided into four parts. First of all we'll present the evidence that the planet is indeed warming, this will be real data from real thermometers. We're aware that some people discount global warming as the product of computer models but this couldn't be further from the truth. Secondly we'll look at how remarkable the recent warming is compared to long-term records of the Earth's climate to see if anything significant is indeed happening. Thirdly, we'll address question "hasn't the climate always changed" to see if any natural variations are causing the climate system to warm. Finally, we'll ask the question "why should you care? "Pictures are worth 1000 words and whether you care about habitat loss here shown graphically in the last few weeks of polar bears life: or this image of a drowned Syrian child trying to escape a war-torn country. The Syrian civil war cannot be blamed wholly upon climate change but the unprecedented drought between 2006 and 2009 that displaced 1.5 million people prior to the start of the war was surely a factor. Finally sea level rise will be the one aspect of climate change that will impact all of us whether we live near the sea or not. 400 million people live within a few metres of the high watermark and within 1 to 200 years they won't be able to live where they are currently.
- So much for the consequences, let's look at the evidence.
- As the main provider of heat for the planet the sun obviously plays a major part in our climate system. When the sun was young, 4.6 billion years ago, it was only around 70% as bright as it is today yet liquid water existed on the Earth's surface throughout most of its history. This points strongly to the existence of other controls on the climate system. Whilst the sun clearly can change its output significantly, such large changes are very slow taking many millions of years. More familiar is the 11 year sunspot cycle but these faster changes are quite minor and can't reasonably explain large changes in the planet's climate. The diagram shows the sun's output over the last four sunspot cycles, together with its intrinsic brightness as measured by satellites. It's evident that the sun's output has actually diminished over the last four cycles with a widely speculated minimum fast approaching. This diagram shows unequivocally that increasing solar output is not the reason for the recent warming trend. In fact the planet should have cooled very slightly over the period.