Thread by @DoomsdayDebunks

IPCC report here, very clear. Have a read of the summary for policy makers near the start of the repot.

ipcc.ch/report/ar6/wg1…

IPCC press briefing again very clearly presented.

The other material is here: ipcc.ch/report/ar6/wg1 - the download link for summary for policy makers doesn't work which is why I linked to the full report. ipcc.ch/report/ar6/wg1…

These are the four scenarios they look at.
SSP1-1.9: Zero emissions for 2050+, ~1.4 °C long term
SSP1-2.6: Zero for 2070+, ~1.8 °C
SSP2-4.5: Low emissions by 2100, ~2.9 °C
SSP2-7.0: Double emissions by 2100, ~3.6 °C
SSP2-8.6: Double emissions by 2050, ~4.4 °C

These are their four scenarios - I've added the temperatures for 2100 and 2050 (marked as mid)

Background info: Current pledges already amongst three lower scenarios - optimistic targets at present close to SSP1-2.6. Highest emissions scenarios no longer plausible.

This shows the contributions to temperature rise from the different components - greenhouse gases, non greenhouse gases and aerosols (cooling effect).

Press briefing summary: If we rapidly reduce greenhouse gas emissions and reach net zero by 2050, extremely likely global warming remains well below 2°C.
Temperature gradually declines to below or around 1.5°C by end of century with an overshoot of no more than 0.1°C above 1.5°C.

Almost all observed warming from late 1800s is human caused.
1. Greenhouse gases: 1°C to 2°C
2. Aerosols etc cooled: 0°C to -0.8°C
3. Total human influence 0.8°C to 1.3°C best estimate 1.07°C
4. Natural drivers -0.1°C to 0.1°C
5. Natural variability -0.2°C to 0.2°C

Most of the CO2 we emit is taken up by land and ocean but less with higher emissions.
- 70%, for zero emissions by ~2050, (~1.4°C),
- 65% for zero emissions by 2070, (~1.8°C)
- 54% for low emissions by 2100 (~2.7°C)
We can forget the other two, as they are implausible scenarios.

Summary of main changes predicted for the various scenarios, added key to each one to help you keep track of which is which scenario.

This is the sea level rise projected to 2300.

D.1.5: we can use CO2 capture to remove CO2 and reverse acidification of the oceans.
D 1.6: Though temperature would respond immediately to CO2 reductions, it would take centuries to millennia for sea levels to reverse course.

To understand impact on extreme events, look at how often we get once per decade event and a once per 50 years event today compared to late 19th century

Added figures converting it to an interval in years - e.g. if it happens 5 times every 10 years that's roughly every 2 yrs.

Similarly for heavy rain and drought.

Final row shows once per decade or per 50 years figure in late C 19 and then with global warming.

The other figures are about the years that exceed C19 once per decade / 50 years figure.

(if I read this right)

The rainfall increases in some areas, decreases in others. What shows as large % increase in a dry area e.g. desert may not be a large amount of actual rain.

Press briefing: Atmosphere can hold more water. More and faster evaporation. Heavier precipitation and monsoon rainfall changes. Global water cycle intensifies.

Rainfall on land expected to increase, but more variable in season and through year, intensifies droughts.

This shows the effect on soil moisture. Again a large % increase in soil moisture in a dry area (or decrease) may not be a big change in actual moisture if it is already very dry.

Hypothetical ramp up quickly to 4 times preindustrial CO2 then decrease at the same rate to pre-industrial.

Never going to go so high - but it's interesting because it shows most of climate is restored with a slight delay but sea level takes longer to restore.
Figure 4.37.

The Equilibrium Climate Sensitivity remains at 3°C as for previous reports, range narrowed to 2.5°C to 4°C from 1.5°C to 4.5°C (TS 3.2)

This is not a scenario - this is instantly doubling CO2 emissions then keeping it at constant level for thousands of years to equilibrium.

So - after all the speculation about the high temperature models and people saying to expect an increase in the ECS - it ends up the same as before with less uncertainty

This is based on
1. models
2. Earth’s energy imbalance,
3. instrumental record
4. paleoclimate proxy records
5. climate feedbacks and how they depend on time and climate state.
They say: "A key advance is the broad agreement across these multiple lines of evidence,"

TS 3.2.1

This report has a novel interactive atlas to look at the projections for your region of the world here. interactive-atlas.ipcc.ch/regional-infor…

Here is where we can expect 0.5 meters of sea level rise by 2100 in the ~1.8°C path (zero emissions 2070+)
interactive-atlas.ipcc.ch/permalink/II46…

This shows the complete range of sea level rises. interactive-atlas.ipcc.ch/permalink/CneQ…

For more detailed sea level planning the Surging Seas website is useful (not from the IPCC report).

1st map: 2 foot rise, at 2060 on the 2 C path, similar to 1.5 C.
ss2.climatecentral.org/#7/27.342/-80.…

2nd map: dates for 10% risk of 5 foot surge on 2C path

ss2.climatecentral.org/#7/26.731/-80.…

I expect they will update Surging Seas based on the IPCC report - meanwhile you can input heights from the IPCC report to Surging Seas to see coastal effects under various sea level rises - note Surging Seas doesn't take account of levees / sea dikes outside the USA.

Extracts from the press conference:

23:56

Paraphrase: The COP26 meeting in Glasgow in November will be a critical milestone. As with running competitions, we need a sprint before the finish.

77:27

Paraphrase:

We know how to mitigate climate change, This is now well understood. The only question is how quickly we can react.

We now have better technical methods.

We also have the financial means to be successful.

But we are not yet there.

80:58
Exceeding 1.5 C is not a catastrophe.

We need to prepare for 1.5 C in coming decades.

We can prevent further warming.

There is no single line to avoid - every increment leads to an increase in frequency and intensity of extreme events.

1:37:26

The report warns that with every additional increment changes become larger.

This can lead to both adaptation (to what we can't prevent) and mitigation (reducing CO2 so the effects don't happen)

95:35 - some people may wonder why the IPCC don't comment on policies.

Some international groups do comment on policy.

However the IPCC are a multilateral assessment body,

The IPCC don't advocate or negate any specific policy of member governments.

All these are lightly paraphrased.

Those are the main points I noticed so far based on the press briefing and a 1st look through of the summary for policy makers, the technical report and a glance into the in depth report. Not read any of them in depth yet, saw for first time after the press briefing. More later.

Forgot to add timescale to Figure 4.37 extract:

Hypothetical ramp up quickly to 4 times preindustrial CO2 then decrease at the same rate to pre-industrial.

Never going to go so high - but shows most climate is restored with slight delay, but sea level takes longer to restore.

Chapter 5: Estimate human agriculture has led to soil carbon losses of about 116 gigatons in the last 12,000 years, estimate 77 gigatons is recoverable by soil improvement.

Background: we emit about 10 gigatons of carbon a year (mostly as CO2).

In chapter 5, discuss particular ecosystems - forests, peatlands, coastal wetlands, ocean sequestration, afforestation, etc. I need to look over that section in detail, this is an article I did before on climate restoration: debunkingdoomsday.quora.com/Dare-to-Hope-C…

They say secondary forest regrowth, restoration of degraded forests and non-forest ecosystems can play a large role in carbon sequestration (high confidence). They also look at other types of CDR (Carbon Dioxide Removal).

Read report for yourself here: ipcc.ch/report/ar6/wg1…

Forgot to add timescale to Figure 4.37 extract:

Hypothetical ramp up quickly to 4 times preindustrial CO2 then decrease at the same rate to pre-industrial.

Never going to go so high - but shows most climate is restored with slight delay, but sea level takes longer to restore.

Chapter 5: Estimate human agriculture has led to soil carbon losses of about 116 gigatons in the last 12,000 years, estimate 77 gigatons is recoverable by soil improvement.

Background: we emit about 10 gigatons of carbon a year (mostly as CO2).

In chapter 5, discuss particular ecosystems - forests, peatlands, coastal wetlands, ocean sequestration, afforestation, etc. I need to look over that section in detail, this is an article I did before on climate restoration: debunkingdoomsday.quora.com/Dare-to-Hope-C…

They say secondary forest regrowth, restoration of degraded forests and non-forest ecosystems can play a large role in carbon sequestration (high confidence). They also look at other types of CDR (Carbon Dioxide Removal).

Read report for yourself here: ipcc.ch/report/ar6/wg1…

I'll be adding more as I get time to explore the new report - very welcome, clearly presented. Lot's of interesting stuff. Will make this into a blog post too.