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I’ve been sparring with a climate change denier on Quora but he is totally blind to reality and just dismisses all evidence of global warming out of hand. Here are some extracts from my latest couple of posts to him, which of course he dismisses.
We’re in unchartered territory with climate change. When temperatures are rising ten times faster than coming out of the last glacial period and the cause is clearly us, there are no precedents on which to base future temperatures, ice quantities and sea levels. We know that CO2 levels are increasing. I think even the deniers accept this. But you can’t have increases in CO2 levels without increases in temperatures for too long unless other factors are playing a major role, and they are not. Solar activity has declined slightly since the 1950s. Volcanic activity is low. The albedo effect, ocean currents, and earth’s axis tilt and orbit have all had little or no effect. Indeed, albedo, tilt and orbit all have only a long term effect which is currently one of cooling. Changes in ocean currents are more a result of climate change rather than a cause of it.
We are emitting an enormous amount of extra CO2 into the atmosphere. This causes temperatures to rise, which causes ice to melt, which causes sea levels to rise. All three of these things are happening; there is nothing surer. We just don’t know the extent of these things into the future. All three are accelerating now. Various projections have been made usually with a fairly wide range. We know that temperatures rose five degrees and sea levels over 400 feet coming out of the last glacial period. So sea level rises are hardly going to stop at a foot or two or three this time, given that temperatures are already up a degree or more and are accelerating and that ice melt is also accelerating. Most CO2 hangs around in the atmosphere for 20-200 years while some is there for up to several hundred thousand years. Therefore, rather than taking the risk, the world is doing something about it by shifting from fossil fuels to renewables albeit slowly.
Detailed global temperature records go back to about 1850. They get better and more detailed all the time and were quite reasonable by 1880. This is where NASA and others start their annual tracking of the adjusted temperature data (it has to be adjusted because weather stations move, usually from centre of town to airports in cooler green areas on the outskirts; and temperature measuring methods and instruments change). See https://climate.nasa.gov/vital-signs/global-temperature/. Note the sharp increase from the 1970s onwards. This is when developing countries got going with industrialisation, adding their CO2 emissions to those of advanced economies.
We are not bereft of weather stations. Key aspects of the atmosphere, land and ocean surface, including temperatures, are recorded every day by more than 10,000 weather stations, 1000 upper air stations, 7000 ships, 1000 drifting and moored buoys, hundreds of weather radars, many weather satellites plus 3000 specially equipped commercial airplanes. Observations are quality controlled by the World Meteorological Organization.
We have good indicators of temperatures before 1850 through earlier readings such as daily UK temperature readings going back to 1772 and monthly back to 1659. Yes, we’ve had satellite data since the 1970s and although this doesn’t measure temperature directly, inferences show an upward temperature trend. Other indicators of temperature include tree growth rings, coral growth, borehole temperatures, sediment in oceans and lakes, cave deposits, fossils, glacier length, ice core samples, and others. From these, we can get pretty good records of temperatures going back 2000 years. This graph shows the results of 11 different scientific studies: https://en.wikipedia.org/wiki/Global_temperature_record#/media/File:2000_Year_Temperature_Comparison.png. Paleoclimatology uses most of these temperature indicators to go back much further. This graph is by Glen Fergus and uses various sources to go back 500 million years: https://en.wikipedia.org/wiki/Paleoclimatology#/media/File:All_palaeotemps.svg. It is probably broadly accurate.
No one is exonerated from reducing carbon. Europe has done best over the last few decades while the US has reduced its too. They have increased in most other countries. After some years of little increase in world emissions, they went up quite a bit in 2018 by about 2-3%. US emissions rose 2.6%, China up 2.2%, India up 7.0% and the EU down 2.0%. But on a per capita basis, the US is way ahead with about 16.5 tons a year, China 7.5 tons, EU about 7 tons and India 1.7 tons. In terms of total CO2 emissions in 2016, China had 10.2 gigatons, US 5.3 gigatons, EU 3.5 gigatons and India 2.4 gigatons.
The negative effects of global warming far outweigh the positive effects. Here is a good summary: https://skepticalscience.com/global-warming-positives-negatives-basic.htm. Climate change is likely to disrupt agriculture due to worse flooding and drought. Deaths due to heatwaves are expected to be five times more than winter deaths prevented. Malaria and diseases from mosquitoes are expected to increase. Ice melt will increase resulting in loss of habitat and water for drinking and agriculture plus sea levels rises will affect food bowl areas and coastal cities. Acidification of oceans will affect the entire ocean food chain. Climate change may result in greener forests but negative effects include “further growth of oxygen poor ocean zones, contamination or exhaustion of fresh water, increased incidence of natural fires, extensive vegetation die-off due to droughts, increased risk of coral extinction, decline in global photoplankton, changes in migration patterns of birds and animals, changes in seasonal periodicity, disruption to food chains and species loss.” Also, we are releasing about twice as much CO2 as the environment can absorb naturally anyway (and would require many trillions of extra trees to fix), thus the build up of CO2 in the atmosphere and the higher temperatures. Climate change could also see mass migration of people (climate refugees) affected by low lying agricultural land and cities, as well as disruptions to global trade, transport, energy supplies, labour markets, banking, finance, investment and insurance. Developing countries could be fighting over water, energy and food, adding to their existing problems.
A number of large studies of the climate science literature plus large surveys of the scientists themselves have found 90-100% agreement (commonly around 97%) with anthropogenic global warming. Surveys of the general population find that a large majority of people agree with the science rather than the denier stuff and it’s not hard to see why. I have been through hundreds of denier sites, pages, articles over many years and have yet to find one that I couldn’t pull apart. People are pretty smart these days and have an abundance of information at their fingertips.
Ice is shrinking at an accelerating rate. Here’s an interesting graph from the University of Washington’s Polar Science Center: https://en.wikipedia.org/wiki/Arctic_sea_ice_decline?fbclid=IwAR0cuDqOLguA2ja9n1C2__oljoO8CH7Q1HvYlyA8rP_kKM7PZtTblDo5aT8#/media/File:Arctic-death-spiral.png. Peak Arctic ice volumes (April) have fallen steadily from about 33,000 cubic km in 1979 to 22,000 cubic km in 2017 or a fall of about a third. Minimum ice levels (September) have fallen more, from 17,000 cubic km to less than 5000 cubic km, or by more than 70%. And the decline in both winter and summer ice volumes is accelerating as the graph clearly shows. More on the Arctic: https://community.windy.com/topic/8382/animated-history-of-arctic-sea-ice-during-the-satellite-era. Note the satellite images showing decreases in ice. The Antarctic is losing about 250 billion tonnes of ice a year, up from 40 billion tonnes a year in the 1980s and the loss is accelerating. Greenland is losing about 200 cubic km of ice a year.
Sea levels rise due to ice melt and also because warmer water expands (see, for example: https://climate.nasa.gov/vital-signs/sea-level/) and they are accelerating. If we don’t reduce our CO2 emissions, sea levels could rise by eight feet by 2100 and fifty feet by 2300 according to this study: https://phys.org/news/2018-10-global-sea-meters.html which is typical of many studies. Under moderate emissions, we might contain sea level rises to a couple of feet by 2100 and ten feet by 2300.