Decoding Confidence and Likelihood in the ipcc fifth Assessment Report



Yüklə 78,06 Kb.
tarix13.11.2017
ölçüsü78,06 Kb.

Confidence and Likelihood in the IPCC Fifth Assessment Report logo of the australian government department of the environment

FACT SHEET

What does the IPCC mean when they use confidence and likelihood’ ?

When the IPCC scientists use the terms ‘confidence’ and ‘likelihood,’ each term has a different and very specific meaning relating to levels of certainty.

When scientists mention ‘confidence’, they are referring to the degree of confidence in being correct. In the case of the IPCC where scientists are analysing global climate, issues such as lack of observational data in certain regions, such as Africa, will affect scientists’ confidence in their findings. When scientists mention ‘likelihood’ they are referring to the probability of an event or outcome occurring.

Confidence

The IPCC Fifth Assessment Report (AR5) confidence levels are based on the evidence (robust, medium and limited) and the degree of scientific agreement (high, medium and low). The combined evidence and agreement results in five levels of confidence (very high, high, medium, low and very low), as shown in the figure below.



figure 1: colour coded confidence levels derived from a combination of level of agreement and evidence.

If an event is given a very high confidence level, there is a combination of high agreement and robust evidence that it will occur.




Likelihood
Standard terms used to define likelihood in the AR5 include:


Term

Likelihood of the outcome

Virtually certain

>99% probability

Extremely likely

>95% probability

Very likely

>90% probability

Likely

>66% probability

More likely than not

>50% probability

About as likely as not

33 to 66% probability

Unlikely

<33% probability

Extremely unlikely

<5% probability

Exceptionally unlikely

<1% probability

If an event is virtually certain, there is a greater than 99% probability that it will occur.



Example: use of the terms confidence’ and likelihood

To understand the use of these terms, consider the following statement based on the AR5’s Summary for Policymakers:



It is very likely that regions of the ocean with high salinity where evaporation dominates have become more saline, while regions of low salinity where precipitation dominates have become fresher since the 1950s. These regional trends in ocean salinity provide indirect evidence that the pattern of evaporation and precipitation over the oceans have changed s been enhanced since the 1950s (medium confidence).

The term ‘very likely in the first part of this statement tells us there is a greater than 90% probability that highly saline regions of the ocean will get more saline, and the term ‘medium confidence’ tells us scientists have either high agreement based on limited evidence; medium agreement based on medium evidence; or low agreement based on robust evidence.
: system -> files -> resources
files -> Şirkət hüquqşunasının fəaliyyətinin psixoloji xüsusiyyətləri
files -> Qəsdən adam öldürmə işləri üzrə məhkəmə təcrübəsi haqqında
files -> Kadrlar şöbəsının mütəxəssısının vəzifə təlimatı Ümumi MÜDDƏalar
files -> Azərbaycan Respublikası Nazirlər Kabinetinin 2013-cü IL 13 avqust tarixli 207 nömrəli qərarı ilə
files -> Sosial müavinətlərin məbləğinin artırılması haqqında
files -> Valideynlərin və digər qohumların uşaqla ünsiyyətdə olmaq hüquqları ilə əlaqədar qanunvericiliyin məhkəmələr tərəfindən tətbiqi təcrübəsi haqqında” Azərbaycan Respublikası Ali Məhkəməsi Plenumunun q ə r a r I
files -> Azərbaycan Respublikasında daimi yaşayan vətəndaşlığı olmayan şəxslərin xüsusi sənədləri haqqında
files -> Ceyhun Əzizov
resources -> Ir544 Barium sulphate method for consecutive determination of radium-226 and radium-228 on the same source
resources -> Department of Sustainability, Environment, Water, Population and Communities


Dostları ilə paylaş:


Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur ©genderi.org 2019
rəhbərliyinə müraciət

    Ana səhifə