By Lauren Casey

PHILADELPHIA (CBS) — Scientists from 13 federal agencies released the fourth National Climate Assessment on Friday, and some of the statistics on the affects of global warming are astounding, confirming a reality that normal weather pattern will continue to become increasingly more erratic.

The global annual average air temperature has increased nearly 2 degrees since 1901, with the last three years being the warmest ever on record.

The report also details that human activities, especially the emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century.

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Thousands of studies conducted by researchers around the world have documented changes in ocean and atmospheric temperatures, melting glaciers, diminishing snow cover, shrinking sea ice, rising sea levels and ocean acidification.

Global average sea level has risen by about 7-8 inches since 1900 with 3 inches of that since 1993.

The frequency of daily tidal flooding is accelerating in more than 25 in Atlantic and Gulf Coast cities.

Sea levels are expected to continue to rise by as low as one foot and up to 4 feet by 2100, though a rise as much as 8 feet cannot be ruled out.

Heat waves have become more frequent nationwide since the 1960s. Large forest fires in the western United States have increased since the 1980s and are projected to continue to increase.

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Annual trends toward earlier spring snow melt and reduced snow pack are already affecting water resources in the western United States.

Another signal of climate change is the increased frequency in heavy rainfall events, with the largest observed changes in the Northeast.