Man-made climate change - a global phenomeon and a regional challenge

Hans von Storch Helmholtz Zentrum GeesthachtGermany

6. December 2013 - "The Impact of Climate Change – Challenges for Latvia and the European Union", Riga

Hans von Storch

1. Climate researcher (in the field since 1971)2. Coastal climate (storms, storm surges, waves;

North and Baltic Sea, North Atlantic); statistical analysis

3. Cooperation with social and cultural scientists since 1992

4. Director of the Institute of Coastal Research of the Helmholtz Zentrum Geesthacht, Germany

5. Professor at Universität Hamburg6. Dr. h.c. Göteborgs Universitet7. Foreign member of Polisch Academy of

Sciences

Mēs vēlētos noskaidrot Jūsu viedokliun uzaicināt Jūs piedalīties nelielā aptaujā:

1. Tiek izdalītas līdz 50 balsu nodošanas ierīcēm.2. Šīs ierīces nav atsevišķi jāieslēdz.3. Kad vēlaties balsot, vienkārši nospiedietatbilstošo numuru.4. Tiklīdz tas ir izdarīts, skaitītājs pārvietojas uz 1.5. Kad ir nobalsojuši visi, tiek parādīts kopējais rezultāts.6. Balsošana ir anonīma. Ir iespējams noteikt, ar kuru ierīci balss ir nodota, taču mēs nevaram noteikt,kuru ierīci Jūs izmantojat.

Anonīma aptauja ar Turning Technology

1. Jā2. Nē3. Vienalga

78%

11%11%

Vai piekrītat piedalīties aptaujā?

Vai klimata pārmaiņas izraisa cilvēki?

1. Esmu pārliecināts, ka pie klimata pārmaiņām, kas vērojamas šobrīd, pārsvarā vainojami cilvēki.2. Es ļoti šaubos, vai pie klimata pārmaiņām pārsvarā ir vainīgi cilvēki.3. Nav viedokļa

38%

13%

50%

Enerģijas politika = klimata politika

1. Es atbalstu enerģijas nozares attīstību bez atomenerģijas, naftas un ogļu pārstrādes.2. Uzskatu, ka pārmaiņas enerģijas politikā vēl nav pārdomātas un ir saistītas ar lielām izmaksām.3. Neuzskatu, ka zinātne irpietiekami gatava pārmaiņām enerģijas politikā.4. Dodu priekšroku citai klimata politikai, piemēram, pielāgošanās pieprasījumam vai ģeoinženierijai.5. Nezinu

11%

33%

0%0%

33%

22%

Ekstrēmi klimata apstākļi

1. Esmu novērojis, ka pēdējo desmitgadu laikā ir palielinājies reģionālo vētru skaits.2. Vētras vienmēr ir bijušas bīstamas, taču es nevaru teikt, ka esmu novērojis to sistemātisku pastiprināšanos vai pavājināšanos.3. Nezinu

55%

0%0%

45%

Zinātnes loma

1. Zinātnei ir jādod padomi politikai, kā risināt problēmas, ja redzams, ka eksistē nopietna problēma.2. Zinātnei ir jādod padomi politikai, kā risināt problēmas, ja zinātnē panākts vienots viedoklis.3. Zinātnei nav jādod padomi, tai ir jādefinē problēma un iespējamie risinājumi.4. Nezinu

50%

0%

42%

8%

Man ir nopietnas bažas par Baltijas jūru. Tam lielākoties ir šādi iemesli:

1. Eitrofikācija (ar barības

vielām)

2. Vides piesārņojums (t. sk.

munīcijas apglabāšana jūrā)

3. Pārlieka nozveja

4. Klimata pārmaiņas

5. Vairāki iemesli

6. Neviens no augstāk

minētajiem iemesliem

7. Nezinu7. N

ezinu

8%

23%

0%

8%

0%

54%

8%

Weather, Climate, Climate Change

• Weather is the sequence of atmospheric states (events) – such as three days of sunshine, or a storm like the present one.

• Weather is predicted by determining the present state and then deriving how this state may develop in the coming days.

• Weather forecasting beyond 10 days, or so, is in principle impossible.

• The future weather may be seen as the outcome of a random events – for forecasts times of more than 10, or so, days – like rolling a dice.

• Weather is a realization of the random process, which is described by ”climate”.

Weather, Climate, Climate Change

• Climate is the statistics of weather, such as the frequency of three days of sunshine in December in Riga, or the probability of a storms like the present one occurring.

• Climate is quantified by determining how often which weather events take place, and then deriving characteristic numbers, such as the maximum wind, the mean temperature etc.

• Possible weather streams can be constructed with climate models, which are conditioned by some influence conditions, such as solar radiation or level of greenhouse gases in the atmosphere.

• Thus, climate can in principle be predicted if the changing influence conditions are known. Example: Next July will be warmer in Riga than in this December.

Predicting weather in 10 days is like forecasting the next outcome of rolling a dice, predicting climate like describing the frequencies of the different outcomes of rolling a dice.

Problem: We can not really predict the future influence conditions, so that we can say only what the climatic consequence may be if the influence conditions are changing in some way. We can construct “scenarios” or “projections” but cannot “predict” climate.

Climate Change – possible causes

Climate, the statistics of weather, can change because of- “internal dynamics” = “smoke without fire”- on time scales of thousands and more years: changes of the orbital position relative to

the sun (ice ages), and other geological factors (movement of continents)- short term natural events - such as solar variations or volcanic eruptions

- man made causes+ release of greenhouse gases+ release of aerosols+ change of land use (incl. urbanization)

Assessing scientific knowledge about climate, climate change and impacts: IPCC

The scientific knowledge about climate, climate change and climate impact is and impacts is regularly assessed

- on the global scale by the International Panel of Climate Change IPCC, with three working groups, on the physics of climate, on the impact and policy options.

- Presently the 5th Assessment report (AR5) is finalized, with the report of Working Group I published in September 2013; the other two in April 2014.

- The reports are usually received very positively – however the 4th Report on impacts (WG II) in 2007 caused major consternation because of a series of errors, which all were biased towards a dramatization.

IPCC: Global temperature development during “instrumental times”

“Detection” of non-natural change

Is the present trend of (speed of change) of the mean global temperature consistent with the concept, that nothing systematic is changing?

No.

One argument: Counting of warmest years in the record of thermometer-based estimates of global mean surface air temperature:

In 2013, among the last 23 years (since 1990) there were the 20 warmest years of all years since 1880 (133 years). The probability for such an event is less than 10-4.

Thus, we detect a change stronger than what would be expected to happen if only stationary variations would be active; thus, an external “new” cause is needed for explaining this clustering

Determining the plausible explanations for non-natural change: “Attribution”

Without the increasing presence of greenhouse gases (GHGs) in the atmosphere, we can not describe the recent warming.

Thus, we attribute the ongoing warming, which was found needing an explanation (detection) to the increasing levels of GHGs in the atmosphere.

These increasing levels are known to be related to man-made emissions of such substances.

Climate scientists agree more and more thata) the world is warming („manifestation“)b) and that this warming can not be explained without referring to increased

GHG levels („attribution“)

Bray

, 201

0

Consensus among climate scientists

Regional Change – the downscaling paradigm

• The global climate is the result of the solar radiation, the geometry of the Earth’s orbit and the rotation – with trade wind systems in the tropics and westerly wind with storms embedded at mid latitudes. No regional detail needed.

• When more detail is added, such as the land-ocean distribution, some large-scale features form, such as the Gulf stream and the mild European climate.

• Regional specifics of climate, such as the difference between Latvia and Sweden, can be explained by combining the large-scale features with physiographic details, in particular the presence of the Baltic Sea and the Norwegian mountains.

• This principle is described by the word “downscaling”, and is employed in regional climate modelling.

BALTEX Assessment of Climate Change for the Baltic Sea basin - BACC

An effort to establish which scientifically legitimized knowledge about climate change and its impacts is available for the Baltic Sea catchment.

In the first report was published 2008. It was compiled by about 80 scientists from 12 countries. In 2014 in BACC the 2nd report will come out, with more than 120 contributing scientists.

The assessments have been accepted by the inter-governmental HELCOM commission as basis for its deliberations.

BACC: Regional change in the pasth

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Principles

→ The assessment is a synthesis of material drawn comprehensively from the available scientifically legitimate literature (e.g. peer reviewed literature, conference proceedings, reports of scientific institutes).

→ Influence or funding from groups with a political, economical or ideological agenda is not allowed; however, questions from such groups are welcome.

→ If a consensus view cannot be found in the above defined literature, this is clearly stated and the differing views are documented. The assessment thus encompasses the knowledge about what scientists agree on but also identify cases of disagreement or knowledge gaps.

Annual and seasonal mean surface air temperature anomalies for the Baltic Sea Basin 1871-2011, Blue colour comprises the Baltic Sea basin to the north of 60°N, and red colour to the south of that latitude.

Air temperature in the Baltic Sea Region, 1871-2011

Warming continued for the last decadeNot in winterLargest in springLargest for northern areas

Data sets Year Winter Spring Summer Autumn

Northern area 0.11 0.10 0.15 0.08 0.10

Southern area 0.08 0.10 0.10 0.04 0.07

1

Linear surface air temperature trends (K per decade) for the period 1871-2011 for the Baltic Sea Basin. Northern area is latitude > 60°N. Bold numbers are significant at the 0.05 level.

Air temperature in the Baltic Sea Region, 1871-2011

Temperature Trends (1982-2011)

23

Observed CRU, EOBS (1982-2011)

95th-%tile of „non-GS“ variability, derived from 2,000-year palaeo-simulations

We detect a warming beyond the range of normal variationsin all seasons

Regional detection in the Baltic Sea Region

Precipitation Trends (1972-2011)

24

Observed CRU, EOBS (1972-2011)

95th-%tile of „non-GHG“ variability, derived from 2,000-year palaeo-simulations

We detect changes in precipitation amounts in winter (DJF), summer (JJA) and in the annual mean (annual), which need external causes for explanation.

Regional detection in the Baltic Sea Region

Range of projected change of: Temperature – at the end of the century

Projections for future regional climate change

Projected temperature trends

26

Projected GS signal, A1B scenario 10 simulations (ENSEMBLES)

The spread of trends of 10 RCM projections

All scenarios suggest that we should presently see a increase in temperature

Range of projected change of: precipitation amount – at the end of the century

Projections for future regional climate change

Projected Precipitation trends

28

The scenarios suggest that we should observe now throughout the year an increase in precipitation amounts, except for summer (JJA).

Projected GS signal, A1B scenario 10 simulations (ENSEMBLES)

The spread of trends of 10 RCM projections

Maximum wind

Projections for future regional climate change

Observed and projected temperature trends (1982-2011)

The observed (grey) trends are mostly consistent with what the regional climate models (green) suggest as response to elevated GHG levels.

However, the observed warming was in all seasons larger than what the models suggested.

Observed CRU, EOBS (1982-2011)

Projected GS signal, A1B scenario 10 simulations (ENSEMBLES)

Regional attribution

Observed 1972-2011 (CRU, EOBS)

Projected GS signal (ENSEMBLES)

Observed (grey) and projected (green) precipitation trends (1972-2011)

The observed changes are in all seasons, except for fall (SON), larger than those suggested by the regional climate models. The observed changes in winter (DJF) , summer (JJA) und fall (SON) are inconsistent with the models’ suggestion.In fall (SON) observation and projection even contradict each other.

Regional attribution

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→ Detection of non-natural influence on regional warming. Can presently be explained by increased greenhouse gas concentrations only. Present trends are consistent with model scenarios.

→ Detection of non-natural component in trends of regional precipitation amounts; present trends much larger than what is anticipated by models; thus no consistent explanation available for the time being.

→ No signal detectable, and to be expected, in storminess.

→ A plausible hypothesis for the inconsistency in precipitation changes, and for the underestimation of the warming trend, is that in the past decades the reduction of aerosol emissions may have played a significant role for the development of the regional climate.

→ For the time being, this hypothesis can not tested as models are insufficient to deal with the effect of man-made aerosols on the regional scale.

Detection and Attribution

Conclusion

1. Climate is changing = the statistics of weather is changing. This change manifests itself mostly in an increase of global mean air temperature, of about 0.8 degree in the past and more to come.

2. The unprecedented increase in greenhouse gases (GHGs) is a plausible major cause behind these changes. GHG is a global driver.

3. The more GHGs are emitted, the larger and faster the change.4. Science has formed a consensus with respect to 1-3.

5. Regionally, also a temperature increase is found, and elevated levels of GHGs can explain this increase.

6. Also precipitation amounts have been found to be beyond the range of natural variations; but these changes can only partly be explained by GHGs. Other factors must be at work. This could be industrial aerosol, which act regionally.

7. A change in storminess can not detected, and is not to be expected.

8. Since the GHG concentration continue to increase, the change of climate is expected to continue as well.