Runs of more than a dozen different GCMs were compared in order to assess the degree of reliability.
Attribution of recent climate change In this article, " climate change " means a change in climate that persists over a sustained period of time. Changes in climate may be due to natural causes, e. Detection does not imply attribution of the detected change to a particular cause.
NASA GISS The graph above shows the average of a set of temperature simulations for the 20th century black linefollowed by projected temperatures for the 21st century based on three greenhouse gas emissions scenarios colored lines.
This projection is relative to global temperatures at the end of the 20th century. Global surface temperature for the past 5. The lastyears are expanded in the lower half of the figure image credit: Physical impacts of climate change Seven of these indicators would be expected to increase in a warming world and observations show that they are, in The impact of global warming and, increasing.
Three would be expected to decrease and they are, in fact, decreasing. Each of the different colored lines in each panel represents an independently analyzed set of data. The data come from many different technologies including weather stationssatellitesweather balloonsships and buoys.
Some of the graphs show a positive trende. Other graphs show a negative trend, e. Evidence of warming is also apparent in living biological systems. With medium confidence see footnote 1IPCC  concluded that human influences had contributed to an increase in heavy precipitation events at the global scale.
Projections of future changes in precipitation show overall increases in the global average, but with substantial shifts in where and how precipitation falls.
Extremely hot nights have doubled in frequency. The area in which extremely hot summers are observed, has increased fold. These changes are not explained by natural variability, and attributed by climate scientists to the influence of anthropogenic climate change.
Heat waves with high humidity pose a big risk to human health while heat waves with low humidity lead to dry conditions that increase wildfires. The mortality from extreme heat is larger than the mortality from hurricanes, lightning, tornadoes, floods, and earthquakes together  See also heat wave.
Tropical cyclones At the global scale, the frequency of tropical cyclones will probably decrease or be unchanged. Some impacts will be beneficial—e.
Retreat of glaciers since A map of the change in thickness of mountain glaciers since Thinning in orange and red, thickening in blue. A map that shows ice concentration on 16 Septemberalong with the extent of the previous record low yellow line and the mid-September median extent black line setting a new record low that was 18 percent smaller than the previous record and nearly 50 percent smaller than the long-term — average.
The cryosphere is made up of areas of the Earth which are covered by snow or ice. Assuming high growth in greenhouse gas emissions SRES A2some models projected that Arctic sea ice in the summer could largely disappear by the end of the 21st century.
Effects of global warming on oceans The role of the oceans in global warming is complex. The oceans serve as a sink for carbon dioxide, taking up much that would otherwise remain in the atmosphere, but increased levels of CO 2 have led to ocean acidification.
Furthermore, as the temperature of the oceans increases, they become less able to absorb excess CO 2. The ocean have also acted as a sink in absorbing extra heat from the atmosphere. Ongoing effects include rising sea levels due to thermal expansion and melting of glaciers and ice sheets, and warming of the ocean surface, leading to increased temperature stratification.
Other possible effects include large-scale changes in ocean circulation. Ocean acidification This map shows changes in the amount of aragonite dissolved in ocean surface waters between the s and the most recent decade — The uptake of human carbon emissions since the year has led to an average decrease in pH of 0.
The effects of ocean acidification on the marine biosphere have yet to be documented. Oxygen depletion The amount of oxygen dissolved in the oceans may decline, with adverse consequences for ocean life.
Future sea level Trends in global average absolute sea level, — Between andthe rate increased above the previous period to 3.
Authors of IPCC AR4 SYR  were uncertain whether the increase in rate from to was due to natural variations in sea level over the time period, or whether it reflected an increase in the underlying long-term trend.
There are two main factors that have contributed to observed sea level rise.The effects of global warming are the environmental and social changes caused (directly or indirectly) by human emissions of greenhouse gases. There is a scientific consensus that climate change is occurring, and that human activities are the primary driver.
. Impacts of Global Warming Global warming is already underway with consequences that must be faced today as well as tomorrow.
Evidence of changes to the Earth's physical, chemical and biological processes is now evident on every continent. What causes climate change (also known as global warming)?
And what are the effects of climate change? Learn the human impact and consequences of climate change for . According to the National Climate Assessment, human influences are the number one cause of global warming, especially the carbon pollution we cause by burning fossil fuels and the pollution.
Nov 15, · Global climate change has already had observable effects on the environment. Glaciers have shrunk, ice on rivers and lakes is breaking up earlier, plant and animal ranges have shifted and trees are flowering sooner.
Impacts of Global Warming Global warming is already underway with consequences that must be faced today as well as tomorrow. Evidence of changes to the Earth's physical, chemical and biological processes is now evident on every continent.