Lecture 10: Vegetative Climate Feedbacks and Mitigation Plans PDF

ENVS3202 Lecture 10: Vegetative Climate Feedbacks and Mitigation Plans Dr. Jin Wu November 20, 2024 School of Biological Sciences, The University of Hong Kong 1 Climate-vegetation interact...

ENVS3202 Lecture 10: Vegetative Climate Feedbacks and Mitigation Plans Dr. Jin Wu November 20, 2024 School of Biological Sciences, The University of Hong Kong 1 Climate-vegetation interactions Impacts Climate change Vegetation change *Physiology *Phenology *Species distribution “Vegetation- Feedbacks mediated climate feedbacks” 2 Vegetative climate feedbacks Global carbon budget (2009 – 2018) GtC yr-1: Source: 10.96 GtC/yr Sink Atmosphe Gigatons of 86% re carbon per Fossil fuel consumption year 44% Lan 29% d 14% Land use change Ocea 23% n Source: CDIAC; NOAA-ESRL; Global Carbon 3  Vegetative climate feedbacks Vegetation changes can also affect the land surface energy balance and hydrological cycle in the climate system. Vegetation: Vegetation: lower reflectance more light in visible light absorbed more light higher absorbed photosynthesis and transpiration heat up Earth’s surface cool down temperature Earth’s surface temperature Bonan. 2008. 4  Outline Vegetative climate feedbacks Global greening impacts Deforestation impacts Climate change mitigation plans Clean energy use Solar geoengineering 5 Global greening Increasing global leaf area index (LAI) from 1982 to 2014 Greening Trends in satellite-observed leaf area index (10-2 m2m- 2 yr-1) Zhu et al. 2016. Nature Climate 6  China and India dominate global greening 34% of the vegetated areas show greening, and China and India lead in the seven greening clusters across six continents Trend in annual average LAI (10 –2 m2 per m2 per decade) Chen et al. 2019. Nature 7  Global greening: land use management China and India lead in greening of the world through land- use management. In India, croplands contribute mostly (82%) to the greening. In China, afforestation and croplands contribute 42% and Chen et 32% to Nature al. 2019. the 8  What drives global greening? 1) Natural greening  Extended growing season length  Enhanced productivity (e.g. CO2 fertilization, Warming) 2) Land use management  Afforestation  Cropland expansions Afforestation Cropland expansions Credit to Shilong Piao and Chi 9  What are the climate feedbacks of global greening? 10  Natural greening: temperature feedback Hypothesis: more greening  higher evapotranspiration  lower air temperature. Methods: Satellite detected greening + process models Observatio ns Earth’s surface air temperature increases ~0.5 ℃ from 1982 to Earth’s greening slowed down the 2012 temperature rise by 0.09 ± 0.02 ℃ Source: Zeng et al. 2017. Nature since 1982 Climate Change; IPCC, Climate 11 Natural greening: soil moisture feedback Global Summe greening r wetter ? Shift in Summe spring r drier phenology Hypothesis: earlier spring phenology  earlier use of soil water Credit to Shilong 12  Natural greening: soil water feedback Spring phenology greening induces the decreasing summer soil water 1.0 -0.15 Summer soil water anomaly (%) Spring LAI 0.8 Spring LAI anomaly (m-2 m-2) Browning Summer soil water Wetting 0.6 -0.10 Fitted soil water 0.4 -0.05 0.2 0.0 0.00 -0.2 Greening 0.05 -0.4 Dryin Early -0.6 0.10 spring leaf g -0.8 onset 0.15 -1.0 1985 1990 1995 2000 2005 2010 Lian et al. 2020. Science 13  Global greening: land use management Natural greening: enhanced productivity per area Managed greening: more green areas with enhanced land use management Afforestation Cropland expansions 14  Afforestation in China Afforestation has been widely implemented since late 1970s Three-North Shelterbelt NFCP: Natural Forest Conservation Development Program, 1978- Program, 1998-2050 2050 GTGP: Grain to Green Program, 15 1999-2010  Afforestation in China: temperature feedback Afforestation decreases daytime land surface temperature (LST) by about 1.1 °C and increases nighttime LST by about 0.2°C. Daytime Nighttime Day- time Night -time Plantation: cool downPlantation: in the daytime warm up in the night time Natural forest Grassla Cropland nd Peng et al. 2014. PNAS 16  Afforestation in China: hydrological feedback Afforestation and vegetation greening lead to the increased precipitation and evapotranspiration, and Pre and ET (mm yr-1 decade-1) the decreased soil moisture Pre ET WY Pre: precipitation; ET: evapotranspiration SM: Soil moisture; LAI: Leaf area index Li et al. 2018. Science Advances 17  Outline Vegetative climate feedbacks Global greening impacts Deforestation impacts Climate change mitigation plans Clean energy use Solar geoengineering 18  Deforestati on Deforestation monitoring over past decades in Ñuflo de Chávez, Bolivia Source: Google earth19 Global deforestation ~3% of global forest cover area Credit to Yan20 Li  What are the climate feedbacks of deforestation? 21  Deforestation: cloud feedback Hypothesis: deforestation less evapotranspiration  less cloud cover and precipitation. 22  Deforestation: cloud feedback Deforestation tends to reduce cloud cover in western Europe Forest cover (Green) Cloud occurrence (Green) France, Landes France, Sologne Teuling et al. 2017. Nat. 23  Deforestation: cloud feedback Deforestation decreases cloud cover around the world America Southeastern Deforestation hotspots in Indonesia 2000-2018 Amazon Credit to Yan Li24  Summary of Part 1 Global greening impacts Natural greening and land use management (e.g. afforestation and crop expansion) both contribute to the recent global greening Natural greening can slow down the global warming while increase the risk of summer droughts Managed greening, e.g. afforestation, can cool down land surface temperature, and increase rainfall events with a cost of decreasing soil moisture Deforestation impacts Deforestation could reduce cloud cover with impacts on local25  Outline Vegetative climate feedbacks Global greening impacts Deforestation impacts Climate change mitigation plans Clean energy use Solar geoengineering 26 Global carbon budget and clean energy use Two major sources of Energy consumption (via fossil anthropogenic CO2 fuel use) dominates the trend emissions since 1950 Energy consumpti on Clean energy use (e.g. wind power, hydropower, solar energy, etc) is an important way to mitigate the Others: Emissions ongoingfrom cement production climate change and gas flaring Source: Houghton et al 2012; Giglio et al 2013; Le Quéré et al 2016; Global Carbon Budget 2016 27 Clean energy use Wind energy Solar energy Hydroenergy Nuclear energy 28  Clean energy use The Paris Agreement aims to Global greenhouse gas limit global warming to well below emissions and rise in 2°C by 2100 temperature Intended Nationally Determined Contributions (INDC) are (intended) reductions in greenhouse gas emissions under the United Nations Framework Convention on Source: Climate Change (UNFCCC). https://medium.com/thebeammagazine/climate-change-challenges-post-u-s-exit-from-paris-climate- 29 agreement-f1dcf9391bdb  Outline Vegetative climate feedbacks Global greening impacts Deforestation impacts Climate change mitigation plans Clean energy use Solar geoengineering 30  Geoengineering Definition: deliberate large-scale manipulation of the global environment to counteract the anthropogenic climate change. Pathway 2: solar Pathway 1: radiation atmospheric CO2 management removal 1) Inject aerosols into 1) Grow more plants in stratosphere lands 2) Increase marine 2) Set up giant reflectors plants in productivity 3) Pump liquid CO2 into 3) orbit etc rocks Shepherd et al. 2009. Geoengineering the climate: Science, governance and uncertainty. 31  Geoengineering Profs. Paul Crutzen and Dr. Tom Wigley suggested to use temporary geoengineering as an emergency response, due to despairing of prompt political response to global warming. Paul Crutzen Tom Wigley (Max Planck Institute; Nobel Prize in(National Center for Atmospheric Research, USA)32  An example: injection of stratospheric aerosols Inject sulfate aerosol precursors into the stratosphere to reduce solar energy reaching the Earth’s surface to counter the global warming. 33 Credit to Alan Robock Stratospheric geoengineering: Benefits GISS Global Average Temperature Anomaly + Anthropogenic Forcing (A1B), 3 Mt SO2/yr Arctic, Geoengineering 5 Mt SO2/yr Tropical, 10 Mt SO2/yr Tropical ends 1.4 Temp Anomaly (°C) from 1951-1980 mean 1.3 Geoengineering 1.2 starts 1.1 1.0 0.9 0.8 0.7 0.6 0.5 0.4 Mitigate 0.3 global 0.2 0.1 warming 0.0 -0.1 -0.2 -0.3 -0.4 -0.5 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 Robock et al., 2008. Journal of 34  Stratospheric geoengineering: Risks acid precipitation under Enhanced Ranges of critical loading of pollutant deposition (including the injection of stratospheric sulfur) for various sites in aerosols Europe [Skeffington, 2006] Critical Load Region (mEq m-2 a-1) Coniferous forests in 13-61 Southern Sweden Deciduous forests in 15-72 Southern Sweden Varied sites in the UK 24-182 Aber in North Wales 32-134 While excess Waterways deposition will in Sweden 1-44 not cause significant acidification, sulfate can still damage human Kravitz et al. 2009. andofecosystem Journal Geophysical35  Summary of Lecture 10 Vegetation changes (e.g., global greening and deforestation) can generate important climate feedbacks by altering the land surface energy balance and hydrological cycle in the climate system. The vegetative buffering on climate change has been weakened, and most of terrestrial ecosystems will soon reach the tipping point. Necessary climate change mitigation plans are needed to help address the climate change issues, with clean energy use being more favored. 36  In-class group presentation 1. Presenters: Ho Cheuk Hei, Lam Yat Fung, and Li Wen Jie Group 15 2. Paper: Zeng et al. (2017). Climate mitigation from vegetation biophysical feedbacks during the past three decades. Nature Climate Change, 7, 432-436. 1. Presenters: Yang Yue and Zhang Jiahui Group 16 2. Paper: Lian et al. (2020). Summer soil drying exacerbated by earlier spring greening of northern vegetation. Science Advances, 6, eaax0255.