climate variability and global change

Question 1

why is solar forcing of climate especially topical?

Answer 1

Satellite instrumental quantification of solar influences Recent scientific advances
Geopolitics
Linkage between solar influence and regional climate (key for interannual to decadal-scale forecasting/ climate prediction)

Question 2

what is geopolitics?

Answer 2

Climate change sceptics cite solar effects as cause of warming and/ or refer to “warmer” periods of the past – e.g. mediaeval warm period

Question 3

when was climate first publicated?

Answer 3

1611- first scientific publication on sunsports. it took some 230 years before cyclic behaviour of sun spots was first documented by Heinrich Schwabe, an amateur

Question 4

how are sunspots and climate joined?

Answer 4

A prolonged near- absence of sunspots 1645 – 1715 remarked on by contemporary astronomers – as were paucity of aurorae
Astronomers Spörer (1887) and Maunder (1890) drew attention to the minimum.
Coincidence of the “prolonged solar minimum” to the coldest excursion of the “Little Ice Age” was pointed out in the 1960’s and pulled together in a “seminal” paper in 1976

Question 5

what did the prolonged solar minimum coincide with?

Answer 5

This coincided with the “great crisis” - unprecedented instability

During the 17th century
-  Decreased agricultural production -  European population decreased by 1/3 (Germany by ½) -  Unprecedented numbers of wars (incl. 30 Years War 1618 - 48)

Question 6

what are sunspots?

Answer 6

Magnetic field lines of sunspots suppress convection and stop plasma from sliding sideways into sunspot

Sunspots are temporary phenomena on the Sun’s photosphere that appear as spots darker than the surrounding areas. They are regions of reduced surface temperature caused by concentrations of magnetic field flux that inhibit convection. Sunspots usually appear in pairs of opposite magnetic polarity. Their number varies according to the approximately 11-year solar cycle.

Question 7

what do sunspots look like?

Answer 7

appear as dark blotches on the Sun in which strong magnetic forces block the hot solar plasma (large-diameter magnetic flux tubes inhibit energy upflow) so sunspots are cooler and darker than their surroundings.

Question 8

what is Faculae?

Answer 8

appear as bright blotches on surface of Sun, put out more radiation than normal and increase solar irradiance

Question 9

how are faculae like sunspots?

Answer 9

Like sunspots, faculae are also the result of magnetic storms, but due to small-diameter magnetic flux tubes enhance energy upflow so T(faculae) ≈ 6200 K

Question 10

how do faculae numbers increase and decrease?

Answer 10

Faculae numbers increase and decrease in concert with sunspots but are much more numerous than sunspots so the heating effects of the faculae exceed (x2) the cooling effects of the sunspots.

Question 11

what does TSI stand for?

Answer 11

total solar irradiance

Question 12

what is evidence of changing in irradiance?

Answer 12

Satellite measurements since 1978 show changes in total solar irradiance (TSI) through solar cycle only 0.1% BUT… UV radiation changes 6-8% short UV and X-ray double
Solar

Question 13

wehre did the ozone changes take place when solar forcing of climate occurred?

Answer 13

2-4% in upper stratosphere

Question 14

how did temperature change due to solar forcing of climate?

Answer 14

2 K range over solar cycle in tropical upper stratosphere
- propagates downwards to 2 K cooling at tropical stratopause at solar minimum
So at Solar Min – lower Stratosphere Equator – Pole Temp gradient is Δ 2 K less

Question 15

how did drive circulation changes due to solar forcing of climate?

Answer 15

Reduced Equator – Pole T gradient – in N. Hem. Winter

- easterly wind anomaly – moves Nth – and weakens westerly Polar Vortex

Question 16

is there evidence for sunspot forcing of climate at multi-year and decadal periods?

Answer 16

“We conclude that the 11-year cycle sometimes seen in climate proxy records is unlikely to be driven by solar forcing, and most likely reflects other natural cycles of the climate system ….

Question 17

what are the proxies for solar activity- what other solar activity is there?

Answer 17

Sun spots are just one manifestation of increased solar activity that includes:

solar flares; mass coronal ejections and associated solar wind

Question 18

how does solar wind increase?

Answer 18

Solar wind emitted from coronal holes on the sun carries magnetic fields which deflect galactic cosmic rays (GCR)

High solar activity causes strong solar wind emission causing a stronger deflection of galactic cosmic rays

so get decreased production of cosmogenic radionuclides

Question 19

what does GCR stand for?

Answer 19

galactic cosmic rays

Question 20

what are GCR?

Answer 20

GCR are mainly high energy particles e.g. protons, neutrons
Solar wind particles are mainly lower energy and mainly affect the upper atmosphere so do not generate the “cosmic” radionuclides 10Be, 14C etc

Question 21

how has solar forcing changed on centernnial timescales?

Answer 21

longer term solar variability does influence climate

Question 22

Do Solar Sunspot cycles influence global or regional climate variability?

Answer 22

are recent cold Northern Hemisphere winters due to a solar minimum? …. Maybe…

Question 23

Is “global warming” due to increased solar activity?

Answer 23

No! – solar variability only drives max 0.2% insolation change - need 1% change - so we need greenhouse gas increase

Question 24

what has caused short term cooling?

Answer 24

Volcanic eruptions have caused major short term cooling

Question 25

how do volcanoes cause cooling?

Answer 25

Plumes from the largest eruptions may ascend at speeds from 10 m/s to > 200m/s and rapidly reach stratospheric heights exceeding 30 km
Subsequently get slow process of gravitational settling

Question 26

what happened in 1991?

Answer 26

Eruption of Mt Pinatubo in the Philippines in June 1991 input larger ash volume to the atmosphere than Krakatoa.

Question 27

where do troicpal thunderstorms top out?

Answer 27

stratosphere

Question 28

what happened within 5 months of Pinatubo volcano?

Answer 28

stratospheric aerosol optical depth from + 40° N to 40° S increases by 2 orders of magnitude.

Question 29

what does underlying warming cause?

Answer 29

Simulations with natural & anthropogenic forcing - only short cooler episodes

Question 30

what does without underlying warming cause?

Answer 30

Simulations with natural forcing only show net cooling effect of eruptions

Question 31

can volcanic and impact events radically change the climate?

Answer 31

yes, yet they are unpredictab;e. however, no known asteroids are heading at us now.

Question 32

what is the hockey stick?

Answer 32

shows the global temperature change in the last 1000 years.

Question 33

has global warming stopped over past 1999-2014?

Answer 33

no-oceans are still warming, sea levels are still rising, ice is still melting.

Question 34

what years are the top 5 warmest?

Answer 34

2016. 2015. 2017, 2018 and 2014

Question 35

how do we date past ice ages?

Answer 35

 Use evidence based on isotopic fractionation The lighter oxygen isotope 16O becomes enriched in snow
The oceans become richer in the heavier isotope 18O
Followed 41,000 year cycle then changed to 100,000 year cycle.

Question 36

what did Milankovitch suggest about the earths orbital?

Answer 36

Milutin Milankovitch (1920) suggested that variations in the Earth’s orbital parameters altered incident solar radiation and its distribution sufficiently to control the timing of the ice ages

Question 37

what did Milankovitch think about isotopes?

Answer 37

Milankovitch’s ideas originally dismissed by physicists because changes in insolation were slight – it then took until 1976 for O isotope records from deep sea cores to prove that these orbital periodicities drove the ice ages. “  The climate is chaotic and only very slight changes are required to “tip” the Earth system from one mode into another.

Question 38

how can the orbital variations be calculated?

Answer 38

The magnitude of changes in insolation due to the orbital variations can be calculated back (and forward) in time by astronomers.

Question 39

what are interglacial cycles?

Answer 39

We can put this together with our marine O isotope and seal level records to look at CO2 variation through the most recent glacial – interglacial cycles

Question 40

what did the interglacial cycles show?

Answer 40

Past natural variability during glacial – interglacial cycles was around 80 ppmv total (from 200 – 280 ppmv)
We passed 400 ppmv in 2013

Question 41

in short term, the main carbon reservoirs which need t be taken into accont in the greenhouse warming debate are?

Answer 41

•   the atmosphere (CO2 gas)
•   the ocean (total dissolved inorganic carbon)
•   the biosphere (organic carbon)
•   the geological reservoir is also important: (fossil fuels !)

Question 42

what is the carbon reservour the atmosphere?

Answer 42

Past natural variability during glacial – interglacial cycles was around 80 ppmv total (from 200 – 280 ppmv)
Increasing and we passed 400 ppmv in May 2013 !  Now – 2019 - at > 410 ppmv

CO2 annual emissions from fossil fuel use and cement manufacture, based on data of British Petroleum

cement is amso causing it to go up, as CaO andclay produce cement. CO2 rpoduced by combusion and calcination.

Question 43

what is the carbon reservoir- the ocean?

Answer 43

The “organic” carbon cycle:
H2O + CO2 <==> CH2O + O2 photosynthesis - dominant in surface waters and respiration - dominant in intermediate and deep waters
This is the “ biological pump ” of carbon into the deep sea target for “geo-engineering” – increase primary production
– increase CO2 draw down from atmosphere The inorganic carbon cycle: Ca2+ + 2HCO3- <==> CaCO3 + CO2 + H2O carbonate formation - dominant in surface waters and dissolution - dominant at depth

  Quick recap on Oceanic Carbon Cycle Equilibration with an atmosphere with enhanced CO2 will cause higher pCO2 throughout the ocean
Result: the ocean, in particular the deep sea, becomes more acidic and more corrosive to carbonates:
CaCO3 + CO2 + H2O ==> Ca2+ + 2HCO3
ocean continues to acidify

Question 44

how can we stop CO2 rises and by when?

Answer 44

CO2 emissions must start to decline before 2100 to reach these targets.

Unless we drastically cut emissions now – we are heading for an overall 300% increase over natural levels.

Question 45

what does RCP stand for?

Answer 45

Representative Concentration Pathways

Question 46

what is the paris agreement?

Answer 46

2015 - 2°C
“to keep global temperature rise this century well below 2°C above pre-industrial levels… and to pursue efforts to limit the T increase even further to 1.5°C”

Question 47

why is the limit of 2 degrees not enough?

Answer 47

“Right now we are facing a man-made disaster of global scale, our greatest threat in thousands of years: climate change.
If we don’t take action, the collapse of our civilisations and the extinction of much of the natural world is on the horizon