Zeng-Zhen Hu

Center for Ocean-Land-Atmosphere Studies4041 Powder Mill Road, Suite 302

Calverton, MD 20705USA

E-mail: hu@cola.iges.org

(CangZhou, Hebei, China, July 10-11, 2009)

How Relevant is Climate Variation in China to Human Activities ?

COLA

Contents of Presentation:(1) What are the observed changes of mean climate and extreme events in China?

(2) What are the projected climate change in China and their uncertainty?

(3) What are the challenges for understanding and predicting the climate change in China?

Observation and simulation: Global Signals:Observation and simulation: Global Signals: (IPCC 2001)(IPCC 2001)

NCAR CCSM3NCAR CCSM3

UKMO ModelUKMO Model

1000 & 140 year global surface T1000 & 140 year global surface T

Observations: Global Signals II Observations: Global Signals II (IPCC 2007)(IPCC 2007)

Projections I: Global Surface Temperature (IPCC 2001)Projections I: Global Surface Temperature (IPCC 2001)

Projections II: Global Surface T: 3 Scenarios (IPCC 2007)Projections II: Global Surface T: 3 Scenarios (IPCC 2007)

Figure 10.18. Changes in extremes based on multi-model simulations from nine global coupled climate models, adapted from Tebaldi et al. (2006). (a) Globally averaged changes in precipitation intensity (defined as the annual total precipitation divided by the number of wet days) for a low (SRES B1), middle (SRES A1B) and high (SRES A2) scenario. (b) Changes in spatial patterns of simulated precipitation intensity between two 20-year means (2080–2099 minus 1980–1999) for the A1B scenario. (c) Globally averaged changes in dry days (defined as the annual maximum number of consecutive dry days). (d) Changes in spatial patterns of simulated dry days between two 20-year means (2080–2099 minus 1980–1999) for the A1B scenario. Solid lines in (a) and (c) are the 10-year smoothed multi-model ensemble means; the envelope indicates the ensemble mean standard deviation. Stippling in (b) and (d) denotes areas where at least five of the nine models concur in determining that the change is statistically significant. Extreme indices are calculated only over land following Frich et al. (2002). Each model’s time series was centred on its 1980 to 1999 average and normalised (rescaled) by its standard deviation computed (after de-trending) over the period 1960 to 2099. The models were then aggregated into an ensemble average, both at the global and at the grid-box level. Thus, changes are given in units of standard deviations.

Projections III: More strong rains and more droughts (IPCC 2007)Projections III: More strong rains and more droughts (IPCC 2007)

For global average, the observed warming trends are clear and the projected warming is even more significant in the global warming scenariosWhat is the climate change in regional scales? For example, are the observed climate variations in China related to global warming or human activities? What is the possible change of the climate in China in the global warming scenarios?

Sensitive of eastern coast regions of China (developed regions) to sea level rising (The Regions Below 50 Meters)

(From: www.eens.aol.com/originals/ red-cares/global-issues)

Annual mean surface T anomalies in China: 1905-2001 (from Tang&Ren, 2005)

19801980

Global annual surface temperature anomalies Global annual surface temperature anomalies (From Prof. R. Lindzen)(From Prof. R. Lindzen)

Annual mean precipitation trends: 1956-2002 (from Ren et al. 2005)

DryingDrying

WettingWetting

WettingWetting

Observed Seasonality: Mean and Differences

(Hu et al. 2003, JGR)

SI=|P|Pmonthmonth-P-Pannualannual/12|/P/12|/Pannualannual

(Measure the homogeneity of (Measure the homogeneity of

the monthly precipitation in a the monthly precipitation in a

year)year)

Seasonality is becoming smaller, particularly in the south&east

Annual surface solar radiation change 1957-2000 (MJ/m*m: Che et al.

2005)

Winter (Nov-Feb) averages of TOMS total aerosol optical depths. Aerosols over the

Gobi desert are mainly due to desert dust, aerosols over the coastal plain have a

large contribution from sulfate. ( NCAR)

Change of annual sunshine time 1956-2002 (hours, Ren et al. 2005)

Annual total cloud amount change 1961-2000 (0.1 part; Ren et al. 2005)

For national average and annul mean of climate change in China:1. Significant warming trend since about 1980;2. Drying in the North and wetting in the South and NW parts; Decreasing seasonality 3. Reducing of total clouds; BUT,4. Decreasing of solar radiation reaching surface and sunshine, may be mainly due to the increase of aerosols/human activities;5. Less transparent of the atmosphere

What are the regional and seasonal differences of the change and are they connected with global warming or human activities?

Observed Seasonal Surface Temperature Trends

2XCO2 -1XCO2 seasonal Surface T (16 CGCM Mean)

SON

MAM

DJF

JJA

Hu et al. JGR 2003Hu et al. JGR 2003

CMIP2 Data and Observations

• (1) 16 CMIP2 CGCMs (http://www-pcmdi.llnl.gov/cmip): • BMRC (Australia), R21, flux adjusted• CSIRO (Australia), R21, flux adjusted• CCCma (Canada), T32, flux adjusted• IAP/LASG (China), R15, flux adjusted • CERFACS (France), T31, NO flux adjusted• LMD/IPSL (France), 3.6x5.6, NO flux adjusted • ECHAM3 (Germany), T21, flux adjusted• ECHAM4 (Germany), T42, flux adjusted• MRI (Japan), 4.0x5.0, flux adjusted • CCSR/NIES (Japan), T21, flux adjusted • INM (Russia), 5.0x4.0, flux adjusted • HadCM2 (UK), 2.5x3.75, flux adjusted • HadCM3 (UK), 2.5x3.75, NO flux adjusted • GFDL (USA), R15, flux adjusted • NCAR (USA), T42, NO flux adjusted• PCM (USA), T42, NO flux adjusted

• (2) CMIP2 Experiment (http://www-pcmdi.llnl.gov/cmip): • Standard gradual increase (1 % per year compound) in CO2

• (3) Observational T & P of 160 stations in China edited by CMA

Observed Seasonal Precipitation Trends

2XCO2 -1XCO2 Seasonal Precipitation (16 CGCM Mean)

JJA

DJF

MAM

SON

Hu et al. JGR 2003Hu et al. JGR 2003

Black Carbon Aerosols: Change the precipitation and temperature patterns (Menon, et al., 2002: Science, 297, 2250-2253)

JJA Temperature ChangeJJA Temperature Change JJA Precipitation ChangeJJA Precipitation Change

Observed JJA T trendsObserved JJA T trends Observed JJA P trendsObserved JJA P trends

Northeastern Asia Monthly P (2*CO2-1*CO2)(Kimoto: GRL, 2005; IPCC 2007, AR4 17 models)

East Asian Winter Monsoon (1% CO2 since 1990, IS92a)

(Hu et al. JGR 2000; IPCC 2001& 2007, ECHAM4/OPYC3)

The mean climate (winter and summer monsoon) in China did have and will have

a significant change

How about the extreme events?

Such as the floors along Yangtze River, typhoons or hurricanes,

as well as the winter storm in the South China?

Observed trends of days with extreme strong rainfall (≥25mm/d): 1951-2000 (From Ding et al., 2006)

Annual mean precipitation trends: 1956-2002 (from Ren et al. 2005)

Yangtze River Discharge

(Germany MPI Models, CGCM and river model)

2XCO2XCO221XCO1XCO22

1860-2004 (From Robert A. Rohde)

Observed typhoon and hurricane change:There is a decrease trend of total storms, but an increase trend of strong hurricane in Atlantic and low-frequency variation in NW Pacific. The trends may be affected by the fact of without accurate data before the satellite observations.

Webster et al. 2005Webster et al. 2005Global storms: DecreaseGlobal storms: Decrease Strong Atlantic Hurricane: IncreaseStrong Atlantic Hurricane: Increase

http://www.wunderground.com/education/nwpac_cat45.gif

NW Pacific: low-frequency variationNW Pacific: low-frequency variation

Simulated typhoon and hurricane change in global warming scenarios (IPCC 2007):Decrease or no significant change of the global total storm numbers;Increase of strong storms in a majority of CGCM global warming simulations. However, it is still a challenge for current climate models in projecting the small scale system change in global warming scenarios, such as typhoon and hurricane.

http://upload.wikimedia.org/wikipedia/en/thumb/f/fd/Hurricane_Intensity_Shift.png/250px-Hurricane_Intensity_Shift.png

From From Thomas R. Knutson and

Robert E. Tuleya (NOAA/GFDL)GFDL)

Is there any contribution of global warming or human activities to the winter storm in the southern China in 2008 ? (no answer yet)

1. How Is the Certainty for these Projections?

2. What Causes the Uncertainty?

Northeastern Asia Monthly P (2*CO2-1*CO2)(Kimoto: GRL, 2005; IPCC 2007, AR4 17 models)

JJA Temperature DJF Temperature

Signal: Mean

Noise: Spread

Signal/Noise: Mean/Spread

LARGELARGE

LARGELARGE

SMALLSMALL

SMALLSMALL

Hu et al. JGR 2003Hu et al. JGR 2003

JJA Precipitation

Signal: Mean

Noise: Spread

Signal/Noise: Mean/Spread

DJF Precipitation

SMALLSMALL

SMALLSMALL

Hu et al. JGR 2003Hu et al. JGR 2003

Uncertainty & Certainty of the Projections

Seasons Precipitation Temperature

Summer Drying in the north and south; wetting in the central

Opposite change to P;

Strong correlation of P & T √

Winter Drying in the north;

Wetting in the south

Warming over the whole country, except a minor cooling in Southwest √

Spring Opposite to the summer pattern

Similar to the winter pattern √

Autumn Drying in almost the whole country, except for the some regions in the central

Similar to the winter pattern √

Why there are so large uncertainty in projecting the regional climate change?

• Imperfect Tools: Models do not or not correctly include the effect of some factors, such as: aerosol, volcano activities, urban effect, land use change, solar activity, nonlinear response and forcing, low resolution, more

• May not fully understand the climate system

Global Climate System

(From: http://www.energysustained.com/global_warming_files/Pic6a.jpg)

Relation of CO2 concentration and global temperature?

Snow cover

Blocking high

Tibet plateau

Land surface process

Monsoon

Indian Ocean

Sub-tropical high pressure

Typhoon

El Niño

Special Challenges for China: No dominate factors in affecting climate of China (Modified from NCC, Prof. Ding)

MJO

Sea Ice

ENSO and Climate Variability in China(Wu, Hu, Kirtman, 2003: J. Climate, 3742-3758)

ENSO summer (CPC/NOAA)

ENSO winter (CPC/NOAA)

No SignalNo Signal

No SignalNo Signal

Impact of El Niño on summer precipitation in China for following year (From NCC/CMA, Prof. Ding)

Strong signal of El

Niño

El Niño events has remarkable effect on summer rainfall in China for following year

Wet over North China and Yangtze basins and dry over Huanghe and Huaihe valleys.

Indian Ocean: Connection of the SSTA with EOF1 &P/T (De-trend & low-passed data; The correlation patterns are similar to the

corresponding patterns of the observed P& T)

(Pronounced warming trends after 1976/77 in almost the whole ocean) (Hu et al. JGR 2003)(Hu et al. JGR 2003)

Connection Between the Pacific/Indian Ocean SSTAand Climate Change in China

(Hu, 1997: JGR, 102, 19403-1941;, Wu, Hu, & Kirtman, 2003: J. Climate,16, 3742-3758)

• Possible mechanism: SST and convective activity Local Hadley cell Intensity and location of subtropical high over

the subtropical western Pacific and China Long-term climate change in China

• Further investigation is necessary.

Black Carbon Aerosols: Change the precipitation and temperature patterns (Menon, et al., 2002: Science, 297, 2250-2253)

JJA Temperature ChangeJJA Temperature Change

JJA Precipitation ChangeJJA Precipitation Change

Discussion 1b: Role of Black Carbon Aerosols(Menon, et al., 2002: Science, 297, 2250-2253)

Tibetan Snow Cover: Positive correlation with subsequent summer precipitation in China (From NCC/CMA, Prof. Ding)

20%20%

Timing of onset of the South China Sea summer monsoon

has a negative correlation with summer precipitation in China

Intensity of the South China Sea summer monsoon has a

negative correlation with summer precipitation in China

(From NCC/CMA, Prof. Ding)

10%10%20%20%

There are so many factors contributing to the climate variations in China, but no one of them are dominant. That results in the difficulty in capturing the climate variation and change in a math-physical model.

However, it is quite sure that warming in the northern part of China is largely attributed to the increase of human activities; The reasons causing the change in the southern are still under debate and exploring the cause is a challenge for current climate models (need higher resolution and more physical, chemical, biological, and society resolved models).

What do we know?•It’s getting warmer in the most parts of China. •Human activities do contribute to it.

What do we know less well? • How does the climate system really work?• How does natural variability interact with anthropogenic forcing? • What is the change of extreme events in global warming scenarios?

What to do?• Better understand the climate system and its forcings.• Better understand the effects on biology, economy and society, and their feedbacks on the climate system.(Modified from the lecture of Prof. Michael Ghil (UCLA))

YES!

Is Climate Variation of China Associated with Global Warming or Human Activities?

Hu, Z.-Z., et al., 2004:. JGR., 109, D21113, doi: 10.1029/2004JD004771.Hu, Z.-Z. and Z. Wu, 2004: Tellus, 56A (2), 112-124.Hu, Z.-Z., et al., 2004: JGR 109 (D10), D10106, doi: 10.1029/2003JD004454.Hu, Z.-Z., S. Yang, and R. Wu, 2003: JGR, 108 (19), 4614, doi: 10.1029/2003JD003651.Wu, R., Z.-Z. Hu, and B. P. Kirtman, 2003: J. Climate, 16 (22), 3742-3758.Hu, Z.-Z., et al., 2001: Clim. Dyn., 17 (5/6), 361-374.Jin, F.-F., Z.-Z. Hu, M. Latif, L. Bengtsson, and E. Roeckner, 2001, GRL, 28 (8), 1539-1542.Hu, Z.-Z., et al., 2000: GRL, 27 (17), 2681-2684.Hu, Z.-Z., L. Bengtsson and K. Arpe, 2000: JGR 105(D4), 4607-4624. Hu, Z.-Z., 1997: JGR, 102(D16), 19403-19412.Hu, Z.-Z. and T. Nitta, 1996: JMSJ, 74(6), 833-844.Nitta, T. and Z.-Z. Hu, 1996: JMSJ, 74(4), 425-445.

Do you think human activity is a significant contributing factor in changing mean global

temperatures?

Source: Doran and Zimmerman, 2009, EOS, 90(3)

Who is Zeng-Zhen HU?!

Education & Work Experience2001-Present, Research scientist, COLA, Maryland, USA2000-2001, Post-doctoral scientist, Center of Ocean-Land-Atmosphere Studies (COLA), Maryland, USA 1998-2000, Visiting senior scientist, Max-Planck Institute for Meteorology (MPI), Hamburg, Germany1995-1996, Visiting associate professor, Center for Climate System Research, the University of Tokyo, Tokyo, Japan 1993-1998, Associated research professor, LASG/IAP/CAS,Beijing 1991-1993, Post-doctoral scientist, Institute of Atmospheric Physics (IAP/CAS), Beijing 1988-1991, Ph. D., Peking University, Beijing

Scientific Output1996-present: About 30 papers in international recornganized journals, and more than 50 Chinese/English papers published in China2001: Contribute author/reviewer of IPCC20011996-present: Reviewers of 13 major international atmospheric journals, DOE, NSF proposals

Further Information:

Dr. Zeng-Zhen HuCenter for Ocean-Land-Atmosphere StudiesInstitute of Global Environment and SocietyCalverton, Maryland 20750, USA Tel: 301-902-1270 (o), Fax: 301-595-9793Email: hu@cola.iges.org;

huorwho@yahoo.com

More Published Papers: ftp://grads.iges.org/pub/hu/paper/

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