Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A cosmic ray-climate link and cloud observations   Despite over 35 years of constant satellite-based measurements of cloud,
reliable evidence of a long-hypothesized link between changes in solar activity
and Earth's cloud cover remains elusive. This work examines evidence of a
cosmic ray cloud link from a range of sources, including satellite-based cloud
measurements and long-term ground-based climatological measurements. The
satellite-based studies can be divided into two categories: 1) monthly to
decadal timescale correlations, and 2) daily timescale epoch-superpositional
(composite) analysis. The latter analyses frequently focus on high-magnitude
reductions in the cosmic ray flux known as Forbush Decrease (FD) events. At
present, two long-term independent global satellite cloud datasets are
available (ISCCP and MODIS). Although the differences between them are
considerable, neither shows evidence of a solar-cloud link at either long or
short timescales. Furthermore, reports of observed correlations between solar
activity and cloud over the 1983 to 1995 period are attributed to the chance
agreement between solar changes and artificially induced cloud trends. It is
possible that the satellite cloud datasets and analysis methods may simply be
too insensitive to detect a small solar signal. Evidence from ground-based
studies suggests that some weak but statistically significant CR-cloud
relationships may exist at regional scales, involving mechanisms related to the
global electric circuit. However, a poor understanding of these mechanisms and
their effects on cloud make the net impacts of such links uncertain. Regardless
of this, it is clear that there is no robust evidence of a widespread link
between the cosmic ray flux and clouds.

7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
35
The categories of this paper are: mtrl-th
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
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The categories of this paper are: eess
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The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
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The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
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The categories of this paper are: cond-mat