Climate Change

Uninhabitable Earth, or merely the “Anthropocene”— humans altering the planet to the point where the changes are visible in the geological record, ringing in a new epoch.

A team led by Earth systems scientists Johan Rockström and Will Steffen developed the concept of “planetary boundaries” (Figure1.1) in 2009. They identified nine major systems where humans were altering fundamental Earth systems—from climate change to land-system change to stratospheric ozone and gave us now-infamous spider graphs summarizing the all-too dire warnings. The green zone is the safe operating space, the yellow represents the zone of uncertainty (increasing risk), and the red is a high-risk zone. The planetary boundary itself lies at the intersection of the green and yellow zones. The control variables have been normalized for the zone of uncertainty; the centre of the figure, therefore, does not represent values of 0 for the control variables. The control variable shown for climate change is atmospheric CO2 concentration. Grey wedges represent processes for which global-level boundaries cannot yet be quantified; these are atmospheric aerosol loading, novel entities, and the functional role of biosphere integrity.

“Planetary boundaries” is a concept involving Earth system processes that contain environmental boundaries.

To discuss the issue about climate change, it is better to consider four types of Carbon dioxide emission (Figure 1.2 (a)) prediction that mentioned by IPCC, RCP2.6 (representative concentration pathways), RCP4.5, RCP6.0, and RCP8.5. Warming will continue beyond 2100 under

Beyond zone of uncertainty (high risk) In zone of uncertainty (increasing risk) Below boundry (safe) Boundary not yet quantified Role of agriculture

Figure 1.1 Current status of the control variables for seven of the planetary boundaries.

The green zone is the safe operating space, the yellow represents the zone of uncertainty (increasing risk), and the red is a high-risk zone. The planetary boundary itself lies at the intersection of the green and yellow zones.

(Source: Will Steffen (2015))

all RCP scenarios except RCP2.6. (Figure 1.2 (b)) Surface temperatures will remain approximately constant at elevated levels for many centuries after a complete cessation of net anthropogenic CO2 emissions. Because the unrecoverable damage from the human pollution hurt Earth environment greatly, the climate is changing, and the temperature must rise, sooner or later. The prediction said by IPCC, a large fraction of anthropogenic climate change resulting from CO2 emissions is irreversible

Figure 1.2 Atmospheric carbon dioxide prediction and global mean surface temperature change prediction

(a) Atmospheric carbon dioxide (CO2) and (b) projected global mean surface temperature change as simu-lated by Earth System Models of Intermediate Complexity (EMICs) for the four Representative Concentra-tion Pathways (RCPs) up to 2300.

(Source: IPCC, Future Climate Change, Risks, and Impacts, https://ar5-syr.ipcc.ch/topic_futurechanges.php)

Figure 1.3 Reasons for Concern at a global scale

Risks associated with Reasons For Concern at a global scale (Figure 1.2) are shown for increasing levels of climate change. The colour shading indicates the additional risk due to climate change when a temperature level is reached and then sustained or exceeded. White indicates no associated impacts are detectable and attributable to climate change. Yellow indicates that associated impacts are both detectable and attributable to climate change with at least medium confidence. Red indicates severe and widespread impacts. Purple, introduced in this assessment, shows that very high risk is indicated by all key risk criteria.

(Source: IPCC, Future Climate Change, Risks, and Impacts, https://ar5-syr.ipcc.ch/topic_futurechanges.php)

on a multi-century to millennial timescale, except in the case of a large net removal of CO2 from the atmosphere over a sustained period. (IPCC, 2014a)

IPCC provided a framework to summarize the critical risks of climate change, Five Reasons For Concern (RFCs), in the Third Assessment Report. They illustrate the implications of warming and adaptation limits for people, economies and ecosystems across sectors and regions. They provide one starting point for evaluating dangerous anthropogenic interference with the climate system. All warming levels are relative to the 1986–2005 period. Adding ~0.6°C to these warming levels roughly gives warming relative to the 1850–1900 period, used here as a proxy for pre-industrial times (right-hand scale). The five RFCs (figure 1.3) are associated with: unique and threatened systems, extreme weather events, distribution of impacts, global aggregate impacts, large-scale singular events.

Stabilization of global average surface temperature does not imply stabilization for all aspects of the climate system. Shifting biomes,

Figure 1.4 Risks to humans and ecosystems from changes in land-based processes as a result of climate change